Index: src/js/_enqueues/vendor/plupload/handlers.js
===================================================================
--- src/js/_enqueues/vendor/plupload/handlers.js	(revision 45788)
+++ src/js/_enqueues/vendor/plupload/handlers.js	(working copy)
@@ -2,42 +2,42 @@
 var topWin = window.dialogArguments || opener || parent || top, uploader, uploader_init;
 
 // progress and success handlers for media multi uploads
-function fileQueued(fileObj) {
+function fileQueued( fileObj ) {
 	// Get rid of unused form
-	jQuery('.media-blank').remove();
+	jQuery( '.media-blank' ).remove();
 
-	var items = jQuery('#media-items').children(), postid = post_id || 0;
+	var items = jQuery( '#media-items' ).children(), postid = post_id || 0;
 
 	// Collapse a single item
 	if ( items.length == 1 ) {
-		items.removeClass('open').find('.slidetoggle').slideUp(200);
+		items.removeClass( 'open' ).find( '.slidetoggle' ).slideUp( 200 );
 	}
 	// Create a progress bar containing the filename
-	jQuery('<div class="media-item">')
+	jQuery( '<div class="media-item">' )
 		.attr( 'id', 'media-item-' + fileObj.id )
-		.addClass('child-of-' + postid)
-		.append('<div class="progress"><div class="percent">0%</div><div class="bar"></div></div>',
-			jQuery('<div class="filename original">').text( ' ' + fileObj.name ))
-		.appendTo( jQuery('#media-items' ) );
+		.addClass( 'child-of-' + postid )
+		.append( '<div class="progress"><div class="percent">0%</div><div class="bar"></div></div>',
+			jQuery( '<div class="filename original">' ).text( ' ' + fileObj.name ))
+		.appendTo( jQuery( '#media-items' ) );
 
 	// Disable submit
-	jQuery('#insert-gallery').prop('disabled', true);
+	jQuery( '#insert-gallery' ).prop( 'disabled', true );
 }
 
 function uploadStart() {
 	try {
 		if ( typeof topWin.tb_remove != 'undefined' )
-			topWin.jQuery('#TB_overlay').unbind('click', topWin.tb_remove);
-	} catch(e){}
+			topWin.jQuery( '#TB_overlay' ).unbind( 'click', topWin.tb_remove );
+	} catch( e ){}
 
 	return true;
 }
 
-function uploadProgress(up, file) {
-	var item = jQuery('#media-item-' + file.id);
+function uploadProgress( up, file ) {
+	var item = jQuery( '#media-item-' + file.id );
 
-	jQuery('.bar', item).width( (200 * file.loaded) / file.size );
-	jQuery('.percent', item).html( file.percent + '%' );
+	jQuery( '.bar', item ).width( ( 200 * file.loaded ) / file.size );
+	jQuery( '.percent', item ).html( file.percent + '%' );
 }
 
 // check to see if a large file failed to upload
@@ -58,45 +58,48 @@
 }
 
 function updateMediaForm() {
-	var items = jQuery('#media-items').children();
+	var items = jQuery( '#media-items' ).children();
 
 	// Just one file, no need for collapsible part
 	if ( items.length == 1 ) {
-		items.addClass('open').find('.slidetoggle').show();
-		jQuery('.insert-gallery').hide();
+		items.addClass( 'open' ).find( '.slidetoggle' ).show();
+		jQuery( '.insert-gallery' ).hide();
 	} else if ( items.length > 1 ) {
-		items.removeClass('open');
+		items.removeClass( 'open' );
 		// Only show Gallery/Playlist buttons when there are at least two files.
-		jQuery('.insert-gallery').show();
+		jQuery( '.insert-gallery' ).show();
 	}
 
 	// Only show Save buttons when there is at least one file.
-	if ( items.not('.media-blank').length > 0 )
-		jQuery('.savebutton').show();
+	if ( items.not( '.media-blank' ).length > 0 )
+		jQuery( '.savebutton' ).show();
 	else
-		jQuery('.savebutton').hide();
+		jQuery( '.savebutton' ).hide();
 }
 
-function uploadSuccess(fileObj, serverData) {
-	var item = jQuery('#media-item-' + fileObj.id);
+function uploadSuccess( fileObj, serverData ) {
+	var item = jQuery( '#media-item-' + fileObj.id );
 
 	// on success serverData should be numeric, fix bug in html4 runtime returning the serverData wrapped in a <pre> tag
-	serverData = serverData.replace(/^<pre>(\d+)<\/pre>$/, '$1');
+	if ( typeof serverData === 'string' ) {
+		serverData = serverData.replace( /^<pre>(\d+)<\/pre>$/, '$1' );
 
-	// if async-upload returned an error message, place it in the media item div and return
-	if ( serverData.match(/media-upload-error|error-div/) ) {
-		item.html(serverData);
-		return;
-	} else {
-		jQuery('.percent', item).html( pluploadL10n.crunching );
+		// if async-upload returned an error message, place it in the media item div and return
+		if ( /media-upload-error|error-div/.test( serverData ) ) {
+			item.html( serverData );
+			return;
+		}
 	}
 
-	prepareMediaItem(fileObj, serverData);
+	item.find( '.percent' ).html( pluploadL10n.crunching );
+
+	prepareMediaItem( fileObj, serverData );
 	updateMediaForm();
 
 	// Increment the counter.
-	if ( post_id && item.hasClass('child-of-' + post_id) )
-		jQuery('#attachments-count').text(1 * jQuery('#attachments-count').text() + 1);
+	if ( post_id && item.hasClass( 'child-of-' + post_id ) ) {
+		jQuery( '#attachments-count' ).text( 1 * jQuery( '#attachments-count' ).text() + 1 );
+	}
 }
 
 function setResize( arg ) {
@@ -116,34 +119,34 @@
 	}
 }
 
-function prepareMediaItem(fileObj, serverData) {
-	var f = ( typeof shortform == 'undefined' ) ? 1 : 2, item = jQuery('#media-item-' + fileObj.id);
+function prepareMediaItem( fileObj, serverData ) {
+	var f = ( typeof shortform == 'undefined' ) ? 1 : 2, item = jQuery( '#media-item-' + fileObj.id );
 	if ( f == 2 && shortform > 2 )
 		f = shortform;
 
 	try {
 		if ( typeof topWin.tb_remove != 'undefined' )
-			topWin.jQuery('#TB_overlay').click(topWin.tb_remove);
-	} catch(e){}
+			topWin.jQuery( '#TB_overlay' ).click( topWin.tb_remove );
+	} catch( e ){}
 
-	if ( isNaN(serverData) || !serverData ) { // Old style: Append the HTML returned by the server -- thumbnail and form inputs
-		item.append(serverData);
-		prepareMediaItemInit(fileObj);
+	if ( isNaN( serverData ) || !serverData ) { // Old style: Append the HTML returned by the server -- thumbnail and form inputs
+		item.append( serverData );
+		prepareMediaItemInit( fileObj );
 	} else { // New style: server data is just the attachment ID, fetch the thumbnail and form html from the server
-		item.load('async-upload.php', {attachment_id:serverData, fetch:f}, function(){prepareMediaItemInit(fileObj);updateMediaForm();});
+		item.load( 'async-upload.php', {attachment_id:serverData, fetch:f}, function(){prepareMediaItemInit( fileObj );updateMediaForm();});
 	}
 }
 
-function prepareMediaItemInit(fileObj) {
-	var item = jQuery('#media-item-' + fileObj.id);
+function prepareMediaItemInit( fileObj ) {
+	var item = jQuery( '#media-item-' + fileObj.id );
 	// Clone the thumbnail as a "pinkynail" -- a tiny image to the left of the filename
-	jQuery('.thumbnail', item).clone().attr('class', 'pinkynail toggle').prependTo(item);
+	jQuery( '.thumbnail', item ).clone().attr( 'class', 'pinkynail toggle' ).prependTo( item );
 
 	// Replace the original filename with the new (unique) one assigned during upload
-	jQuery('.filename.original', item).replaceWith( jQuery('.filename.new', item) );
+	jQuery( '.filename.original', item ).replaceWith( jQuery( '.filename.new', item ) );
 
 	// Bind AJAX to the new Delete button
-	jQuery('a.delete', item).click(function(){
+	jQuery( 'a.delete', item ).click( function(){
 		// Tell the server to delete it. TODO: handle exceptions
 		jQuery.ajax({
 			url: ajaxurl,
@@ -152,9 +155,9 @@
 			error: deleteError,
 			id: fileObj.id,
 			data: {
-				id : this.id.replace(/[^0-9]/g, ''),
+				id : this.id.replace(/[^0-9]/g, '' ),
 				action : 'trash-post',
-				_ajax_nonce : this.href.replace(/^.*wpnonce=/,'')
+				_ajax_nonce : this.href.replace(/^.*wpnonce=/,'' )
 			}
 		});
 		return false;
@@ -161,7 +164,7 @@
 	});
 
 	// Bind AJAX to the new Undo button
-	jQuery('a.undo', item).click(function(){
+	jQuery( 'a.undo', item ).click( function(){
 		// Tell the server to untrash it. TODO: handle exceptions
 		jQuery.ajax({
 			url: ajaxurl,
@@ -168,25 +171,25 @@
 			type: 'post',
 			id: fileObj.id,
 			data: {
-				id : this.id.replace(/[^0-9]/g,''),
+				id : this.id.replace(/[^0-9]/g,'' ),
 				action: 'untrash-post',
-				_ajax_nonce: this.href.replace(/^.*wpnonce=/,'')
+				_ajax_nonce: this.href.replace(/^.*wpnonce=/,'' )
 			},
 			success: function( ){
 				var type,
-					item = jQuery('#media-item-' + fileObj.id);
+					item = jQuery( '#media-item-' + fileObj.id );
 
-				if ( type = jQuery('#type-of-' + fileObj.id).val() )
-					jQuery('#' + type + '-counter').text(jQuery('#' + type + '-counter').text()-0+1);
+				if ( type = jQuery( '#type-of-' + fileObj.id ).val() )
+					jQuery( '#' + type + '-counter' ).text( jQuery( '#' + type + '-counter' ).text()-0+1 );
 
-				if ( post_id && item.hasClass('child-of-'+post_id) )
-					jQuery('#attachments-count').text(jQuery('#attachments-count').text()-0+1);
+				if ( post_id && item.hasClass( 'child-of-'+post_id ) )
+					jQuery( '#attachments-count' ).text( jQuery( '#attachments-count' ).text()-0+1 );
 
-				jQuery('.filename .trashnotice', item).remove();
-				jQuery('.filename .title', item).css('font-weight','normal');
-				jQuery('a.undo', item).addClass('hidden');
-				jQuery('.menu_order_input', item).show();
-				item.css( {backgroundColor:'#ceb'} ).animate( {backgroundColor: '#fff'}, { queue: false, duration: 500, complete: function(){ jQuery(this).css({backgroundColor:''}); } }).removeClass('undo');
+				jQuery( '.filename .trashnotice', item ).remove();
+				jQuery( '.filename .title', item ).css( 'font-weight','normal' );
+				jQuery( 'a.undo', item ).addClass( 'hidden' );
+				jQuery( '.menu_order_input', item ).show();
+				item.css( {backgroundColor:'#ceb'} ).animate( {backgroundColor: '#fff'}, { queue: false, duration: 500, complete: function(){ jQuery( this ).css({backgroundColor:''}); } }).removeClass( 'undo' );
 			}
 		});
 		return false;
@@ -193,138 +196,139 @@
 	});
 
 	// Open this item if it says to start open (e.g. to display an error)
-	jQuery('#media-item-' + fileObj.id + '.startopen').removeClass('startopen').addClass('open').find('slidetoggle').fadeIn();
+	jQuery( '#media-item-' + fileObj.id + '.startopen' ).removeClass( 'startopen' ).addClass( 'open' ).find( 'slidetoggle' ).fadeIn();
 }
 
 // generic error message
-function wpQueueError(message) {
-	jQuery('#media-upload-error').show().html( '<div class="error"><p>' + message + '</p></div>' );
+function wpQueueError( message ) {
+	jQuery( '#media-upload-error' ).show().html( '<div class="error"><p>' + message + '</p></div>' );
 }
 
 // file-specific error messages
-function wpFileError(fileObj, message) {
-	itemAjaxError(fileObj.id, message);
+function wpFileError( fileObj, message ) {
+	itemAjaxError( fileObj.id, message );
 }
 
-function itemAjaxError(id, message) {
-	var item = jQuery('#media-item-' + id), filename = item.find('.filename').text(), last_err = item.data('last-err');
+function itemAjaxError( id, message ) {
+	var item = jQuery( '#media-item-' + id ), filename = item.find( '.filename' ).text(), last_err = item.data( 'last-err' );
 
 	if ( last_err == id ) // prevent firing an error for the same file twice
 		return;
 
-	item.html('<div class="error-div">' +
+	item.html( '<div class="error-div">' +
 				'<a class="dismiss" href="#">' + pluploadL10n.dismiss + '</a>' +
-				'<strong>' + pluploadL10n.error_uploading.replace('%s', jQuery.trim(filename)) + '</strong> ' +
+				'<strong>' + pluploadL10n.error_uploading.replace( '%s', jQuery.trim( filename )) + '</strong> ' +
 				message +
-				'</div>').data('last-err', id);
+				'</div>' ).data( 'last-err', id );
 }
 
-function deleteSuccess(data) {
+function deleteSuccess( data ) {
 	var type, id, item;
 	if ( data == '-1' )
-		return itemAjaxError(this.id, 'You do not have permission. Has your session expired?');
+		return itemAjaxError( this.id, 'You do not have permission. Has your session expired?' );
 
 	if ( data == '0' )
-		return itemAjaxError(this.id, 'Could not be deleted. Has it been deleted already?');
+		return itemAjaxError( this.id, 'Could not be deleted. Has it been deleted already?' );
 
 	id = this.id;
-	item = jQuery('#media-item-' + id);
+	item = jQuery( '#media-item-' + id );
 
 	// Decrement the counters.
-	if ( type = jQuery('#type-of-' + id).val() )
-		jQuery('#' + type + '-counter').text( jQuery('#' + type + '-counter').text() - 1 );
+	if ( type = jQuery( '#type-of-' + id ).val() )
+		jQuery( '#' + type + '-counter' ).text( jQuery( '#' + type + '-counter' ).text() - 1 );
 
-	if ( post_id && item.hasClass('child-of-'+post_id) )
-		jQuery('#attachments-count').text( jQuery('#attachments-count').text() - 1 );
+	if ( post_id && item.hasClass( 'child-of-'+post_id ) )
+		jQuery( '#attachments-count' ).text( jQuery( '#attachments-count' ).text() - 1 );
 
-	if ( jQuery('form.type-form #media-items').children().length == 1 && jQuery('.hidden', '#media-items').length > 0 ) {
-		jQuery('.toggle').toggle();
-		jQuery('.slidetoggle').slideUp(200).siblings().removeClass('hidden');
+	if ( jQuery( 'form.type-form #media-items' ).children().length == 1 && jQuery( '.hidden', '#media-items' ).length > 0 ) {
+		jQuery( '.toggle' ).toggle();
+		jQuery( '.slidetoggle' ).slideUp( 200 ).siblings().removeClass( 'hidden' );
 	}
 
 	// Vanish it.
-	jQuery('.toggle', item).toggle();
-	jQuery('.slidetoggle', item).slideUp(200).siblings().removeClass('hidden');
-	item.css( {backgroundColor:'#faa'} ).animate( {backgroundColor:'#f4f4f4'}, {queue:false, duration:500} ).addClass('undo');
+	jQuery( '.toggle', item ).toggle();
+	jQuery( '.slidetoggle', item ).slideUp( 200 ).siblings().removeClass( 'hidden' );
+	item.css( {backgroundColor:'#faa'} ).animate( {backgroundColor:'#f4f4f4'}, {queue:false, duration:500} ).addClass( 'undo' );
 
-	jQuery('.filename:empty', item).remove();
-	jQuery('.filename .title', item).css('font-weight','bold');
-	jQuery('.filename', item).append('<span class="trashnotice"> ' + pluploadL10n.deleted + ' </span>').siblings('a.toggle').hide();
-	jQuery('.filename', item).append( jQuery('a.undo', item).removeClass('hidden') );
-	jQuery('.menu_order_input', item).hide();
+	jQuery( '.filename:empty', item ).remove();
+	jQuery( '.filename .title', item ).css( 'font-weight','bold' );
+	jQuery( '.filename', item ).append( '<span class="trashnotice"> ' + pluploadL10n.deleted + ' </span>' ).siblings( 'a.toggle' ).hide();
+	jQuery( '.filename', item ).append( jQuery( 'a.undo', item ).removeClass( 'hidden' ) );
+	jQuery( '.menu_order_input', item ).hide();
 
 	return;
 }
 
 function deleteError() {
-	// TODO
 }
 
 function uploadComplete() {
-	jQuery('#insert-gallery').prop('disabled', false);
+	jQuery( '#insert-gallery' ).prop( 'disabled', false );
 }
 
-function switchUploader(s) {
+function switchUploader( s ) {
 	if ( s ) {
-		deleteUserSetting('uploader');
-		jQuery('.media-upload-form').removeClass('html-uploader');
+		deleteUserSetting( 'uploader' );
+		jQuery( '.media-upload-form' ).removeClass( 'html-uploader' );
 
-		if ( typeof(uploader) == 'object' )
+		if ( typeof( uploader ) == 'object' )
 			uploader.refresh();
 	} else {
-		setUserSetting('uploader', '1'); // 1 == html uploader
-		jQuery('.media-upload-form').addClass('html-uploader');
+		setUserSetting( 'uploader', '1' ); // 1 == html uploader
+		jQuery( '.media-upload-form' ).addClass( 'html-uploader' );
 	}
 }
 
-function uploadError(fileObj, errorCode, message, uploader) {
+function uploadError( fileObj, errorCode, message, up ) {
 	var hundredmb = 100 * 1024 * 1024, max;
 
-	switch (errorCode) {
+	switch ( errorCode ) {
 		case plupload.FAILED:
-			wpFileError(fileObj, pluploadL10n.upload_failed);
+			wpFileError( fileObj, pluploadL10n.upload_failed );
 			break;
 		case plupload.FILE_EXTENSION_ERROR:
-			wpFileExtensionError( uploader, fileObj, pluploadL10n.invalid_filetype );
+			wpFileExtensionError( up, fileObj, pluploadL10n.invalid_filetype );
 			break;
 		case plupload.FILE_SIZE_ERROR:
-			uploadSizeError(uploader, fileObj);
+			uploadSizeError( up, fileObj );
 			break;
 		case plupload.IMAGE_FORMAT_ERROR:
-			wpFileError(fileObj, pluploadL10n.not_an_image);
+			wpFileError( fileObj, pluploadL10n.not_an_image );
 			break;
 		case plupload.IMAGE_MEMORY_ERROR:
-			wpFileError(fileObj, pluploadL10n.image_memory_exceeded);
+			wpFileError( fileObj, pluploadL10n.image_memory_exceeded );
 			break;
 		case plupload.IMAGE_DIMENSIONS_ERROR:
-			wpFileError(fileObj, pluploadL10n.image_dimensions_exceeded);
+			wpFileError( fileObj, pluploadL10n.image_dimensions_exceeded );
 			break;
 		case plupload.GENERIC_ERROR:
-			wpQueueError(pluploadL10n.upload_failed);
+			wpQueueError( pluploadL10n.upload_failed );
 			break;
 		case plupload.IO_ERROR:
-			max = parseInt( uploader.settings.filters.max_file_size, 10 );
+			max = parseInt( up.settings.filters.max_file_size, 10 );
 
-			if ( max > hundredmb && fileObj.size > hundredmb )
-				wpFileError( fileObj, pluploadL10n.big_upload_failed.replace('%1$s', '<a class="uploader-html" href="#">').replace('%2$s', '</a>') );
-			else
-				wpQueueError(pluploadL10n.io_error);
+			if ( max > hundredmb && fileObj.size > hundredmb ) {
+				wpFileError( fileObj, pluploadL10n.big_upload_failed.replace( '%1$s', '<a class="uploader-html" href="#">' ).replace( '%2$s', '</a>' ) );
+			} else {
+				wpQueueError( pluploadL10n.io_error );
+			}
+
 			break;
 		case plupload.HTTP_ERROR:
-			wpQueueError(pluploadL10n.http_error);
+			wpQueueError( pluploadL10n.http_error );
 			break;
 		case plupload.INIT_ERROR:
-			jQuery('.media-upload-form').addClass('html-uploader');
+			jQuery( '.media-upload-form' ).addClass( 'html-uploader' );
 			break;
 		case plupload.SECURITY_ERROR:
-			wpQueueError(pluploadL10n.security_error);
+			wpQueueError( pluploadL10n.security_error );
 			break;
 /*		case plupload.UPLOAD_ERROR.UPLOAD_STOPPED:
 		case plupload.UPLOAD_ERROR.FILE_CANCELLED:
-			jQuery('#media-item-' + fileObj.id).remove();
+			jQuery( '#media-item-' + fileObj.id ).remove();
 			break;*/
 		default:
-			wpFileError(fileObj, pluploadL10n.default_error);
+			wpFileError( fileObj, pluploadL10n.default_error );
 	}
 }
 
@@ -331,7 +335,7 @@
 function uploadSizeError( up, file ) {
 	var message, errorDiv;
 
-	message = pluploadL10n.file_exceeds_size_limit.replace('%s', file.name);
+	message = pluploadL10n.file_exceeds_size_limit.replace( '%s', file.name );
 
 	// Construct the error div.
 	errorDiv = jQuery( '<div />' )
@@ -345,51 +349,59 @@
 		);
 
 	// Append the error.
-	jQuery('#media-items').append( errorDiv );
-	up.removeFile(file);
+	jQuery( '#media-items' ).append( errorDiv );
+	up.removeFile( file );
 }
 
 function wpFileExtensionError( up, file, message ) {
-	jQuery('#media-items').append('<div id="media-item-' + file.id + '" class="media-item error"><p>' + message + '</p></div>');
-	up.removeFile(file);
+	jQuery( '#media-items' ).append( '<div id="media-item-' + file.id + '" class="media-item error"><p>' + message + '</p></div>' );
+	up.removeFile( file );
 }
 
-jQuery(document).ready(function($){
-	$('.media-upload-form').bind('click.uploader', function(e) {
-		var target = $(e.target), tr, c;
+jQuery( document ).ready( function( $ ) {
+	var tryAgainCount = {};
+	var tryAgain;
 
-		if ( target.is('input[type="radio"]') ) { // remember the last used image size and alignment
-			tr = target.closest('tr');
+	$( '.media-upload-form' ).bind( 'click.uploader', function( e ) {
+		var target = $( e.target ), tr, c;
 
-			if ( tr.hasClass('align') )
-				setUserSetting('align', target.val());
-			else if ( tr.hasClass('image-size') )
-				setUserSetting('imgsize', target.val());
+		if ( target.is( 'input[type="radio"]' ) ) { // remember the last used image size and alignment
+			tr = target.closest( 'tr' );
 
-		} else if ( target.is('button.button') ) { // remember the last used image link url
+			if ( tr.hasClass( 'align' ) )
+				setUserSetting( 'align', target.val() );
+			else if ( tr.hasClass( 'image-size' ) )
+				setUserSetting( 'imgsize', target.val() );
+
+		} else if ( target.is( 'button.button' ) ) { // remember the last used image link url
 			c = e.target.className || '';
-			c = c.match(/url([^ '"]+)/);
+			c = c.match( /url([^ '"]+)/ );
 
 			if ( c && c[1] ) {
-				setUserSetting('urlbutton', c[1]);
-				target.siblings('.urlfield').val( target.data('link-url') );
+				setUserSetting( 'urlbutton', c[1] );
+				target.siblings( '.urlfield' ).val( target.data( 'link-url' ) );
 			}
-		} else if ( target.is('a.dismiss') ) {
-			target.parents('.media-item').fadeOut(200, function(){
-				$(this).remove();
-			});
-		} else if ( target.is('.upload-flash-bypass a') || target.is('a.uploader-html') ) { // switch uploader to html4
-			$('#media-items, p.submit, span.big-file-warning').css('display', 'none');
-			switchUploader(0);
+		} else if ( target.is( 'a.dismiss' ) ) {
+			target.parents( '.media-item' ).fadeOut( 200, function() {
+				$( this ).remove();
+			} );
+		} else if ( target.is( '.upload-flash-bypass a' ) || target.is( 'a.uploader-html' ) ) { // switch uploader to html4
+			$( '#media-items, p.submit, span.big-file-warning' ).css( 'display', 'none' );
+			switchUploader( 0 );
 			e.preventDefault();
-		} else if ( target.is('.upload-html-bypass a') ) { // switch uploader to multi-file
-			$('#media-items, p.submit, span.big-file-warning').css('display', '');
-			switchUploader(1);
+		} else if ( target.is( '.upload-html-bypass a' ) ) { // switch uploader to multi-file
+			$( '#media-items, p.submit, span.big-file-warning' ).css( 'display', '' );
+			switchUploader( 1 );
 			e.preventDefault();
-		} else if ( target.is('a.describe-toggle-on') ) { // Show
-			target.parent().addClass('open');
-			target.siblings('.slidetoggle').fadeIn(250, function(){
-				var S = $(window).scrollTop(), H = $(window).height(), top = $(this).offset().top, h = $(this).height(), b, B;
+		} else if ( target.is( 'a.describe-toggle-on' ) ) { // Show
+			target.parent().addClass( 'open' );
+			target.siblings( '.slidetoggle' ).fadeIn( 250, function() {
+				var S = $( window ).scrollTop(),
+					H = $( window ).height(),
+					top = $( this ).offset().top,
+					h = $( this ).height(),
+					b,
+					B;
 
 				if ( H && top && h ) {
 					b = top + h;
@@ -397,65 +409,121 @@
 
 					if ( b > B ) {
 						if ( b - B < top - S )
-							window.scrollBy(0, (b - B) + 10);
+							window.scrollBy( 0, ( b - B ) + 10 );
 						else
-							window.scrollBy(0, top - S - 40);
+							window.scrollBy( 0, top - S - 40 );
 					}
 				}
-			});
+			} );
+
 			e.preventDefault();
-		} else if ( target.is('a.describe-toggle-off') ) { // Hide
-			target.siblings('.slidetoggle').fadeOut(250, function(){
-				target.parent().removeClass('open');
-			});
+		} else if ( target.is( 'a.describe-toggle-off' ) ) { // Hide
+			target.siblings( '.slidetoggle' ).fadeOut( 250, function() {
+				target.parent().removeClass( 'open' );
+			} );
+
 			e.preventDefault();
 		}
 	});
 
-	// init and set the uploader
-	uploader_init = function() {
-		var isIE = navigator.userAgent.indexOf('Trident/') != -1 || navigator.userAgent.indexOf('MSIE ') != -1;
+	// Attempt to create image sub-sizes when an image was uploaded successfully
+	// but the server responded with HTTP 500 error.
+	tryAgain = function( up, error ) {
+		var file = error.file;
+		var times;
+		var message;
 
-		// Make sure flash sends cookies (seems in IE it does whitout switching to urlstream mode)
-		if ( ! isIE && 'flash' === plupload.predictRuntime( wpUploaderInit ) &&
-			( ! wpUploaderInit.required_features || ! wpUploaderInit.required_features.hasOwnProperty( 'send_binary_string' ) ) ) {
+		if ( ! file || ! file.id ) {
+			wpQueueError( error.message || pluploadL10n.http_error );
+			return;
+		}
 
-			wpUploaderInit.required_features = wpUploaderInit.required_features || {};
-			wpUploaderInit.required_features.send_binary_string = true;
+		times = tryAgainCount[ file.id ];
+
+		if ( times && times > 3 ) {
+			wpQueueError( error.message || pluploadL10n.http_error );
+			return;
 		}
 
-		uploader = new plupload.Uploader(wpUploaderInit);
+		if ( ! times ) {
+			tryAgainCount[ file.id ] = 1;
+		} else {
+			tryAgainCount[ file.id ] = ++times;
+		}
 
-		$('#image_resize').bind('change', function() {
-			var arg = $(this).prop('checked');
+		// Try to create the missing image sizes three times.
+		$.ajax({
+			type: 'post',
+			url: ajaxurl,
+			dataType: 'json',
+			data: {
+				action: 'media-create-image-subsizes',
+				_wpnonce: wpUploaderInit.multipart_params._wpnonce,
+				_wp_temp_image_ref: file.id,
+				_legasy_support: 'true',
+			}
+		}).done( function( response ) {
+			var message;
 
+			if ( response.success ) {
+				uploadSuccess( file, response.data.id );
+			} else {
+				if ( response.data && response.data.message ) {
+					message = response.data.message;
+				} else if ( _.isString( response ) ) {
+					// Can be error message coming from PHP that may have few simple HTML tags. Remove them.
+					message = response.replace( /<\/?[a-zA-Z][^>]*>/g, '' );
+					message = _.escape( message );
+				}
+
+				wpQueueError( message || pluploadL10n.http_error );
+			}
+		}).fail( function( jqXHR ) {
+			// If another HTTP 500 error, try again up to 3 times.
+			if ( jqXHR.status === 500 ) {
+				tryAgain( up, error );
+				return;
+			}
+
+			wpQueueError( jqXHR.responseText || pluploadL10n.http_error );
+		});
+	}
+
+	// init and set the uploader
+	uploader_init = function() {
+		uploader = new plupload.Uploader( wpUploaderInit );
+
+		$( '#image_resize' ).bind( 'change', function() {
+			var arg = $( this ).prop( 'checked' );
+
 			setResize( arg );
 
 			if ( arg )
-				setUserSetting('upload_resize', '1');
+				setUserSetting( 'upload_resize', '1' );
 			else
-				deleteUserSetting('upload_resize');
+				deleteUserSetting( 'upload_resize' );
 		});
 
-		uploader.bind('Init', function(up) {
-			var uploaddiv = $('#plupload-upload-ui');
+		uploader.bind( 'Init', function( up ) {
+			var uploaddiv = $( '#plupload-upload-ui' );
 
-			setResize( getUserSetting('upload_resize', false) );
+			setResize( getUserSetting( 'upload_resize', false ) );
 
-			if ( up.features.dragdrop && ! $(document.body).hasClass('mobile') ) {
-				uploaddiv.addClass('drag-drop');
-				$('#drag-drop-area').on('dragover.wp-uploader', function(){ // dragenter doesn't fire right :(
-					uploaddiv.addClass('drag-over');
-				}).on('dragleave.wp-uploader, drop.wp-uploader', function(){
-					uploaddiv.removeClass('drag-over');
+			if ( up.features.dragdrop && ! $( document.body ).hasClass( 'mobile' ) ) {
+				uploaddiv.addClass( 'drag-drop' );
+
+				$( '#drag-drop-area' ).on( 'dragover.wp-uploader', function() { // dragenter doesn't fire right :(
+					uploaddiv.addClass( 'drag-over' );
+				}).on( 'dragleave.wp-uploader, drop.wp-uploader', function() {
+					uploaddiv.removeClass( 'drag-over' );
 				});
 			} else {
-				uploaddiv.removeClass('drag-drop');
-				$('#drag-drop-area').off('.wp-uploader');
+				uploaddiv.removeClass( 'drag-drop' );
+				$( '#drag-drop-area' ).off( '.wp-uploader' );
 			}
 
 			if ( up.runtime === 'html4' ) {
-				$('.upload-flash-bypass').hide();
+				$( '.upload-flash-bypass' ).hide();
 			}
 		});
 
@@ -465,8 +533,8 @@
 
 		uploader.init();
 
-		uploader.bind('FilesAdded', function( up, files ) {
-			$('#media-upload-error').empty();
+		uploader.bind( 'FilesAdded', function( up, files ) {
+			$( '#media-upload-error' ).empty();
 			uploadStart();
 
 			plupload.each( files, function( file ) {
@@ -477,29 +545,53 @@
 			up.start();
 		});
 
-		uploader.bind('UploadFile', function(up, file) {
-			fileUploading(up, file);
+		uploader.bind( 'UploadFile', function( up, file ) {
+			fileUploading( up, file );
 		});
 
-		uploader.bind('UploadProgress', function(up, file) {
-			uploadProgress(up, file);
+		uploader.bind( 'UploadProgress', function( up, file ) {
+			uploadProgress( up, file );
 		});
 
-		uploader.bind('Error', function(up, err) {
-			uploadError(err.file, err.code, err.message, up);
+		uploader.bind( 'Error', function( up, error ) {
+			var isImage = error.file && error.file.type && error.file.type.indexOf( 'image/' ) === 0;
+			var status  = error && error.status;
+
+			// If the file is an image and the error is HTTP 500 try to create sub-sizes again.
+			if ( status === 500 && isImage ) {
+				tryAgain( up, error );
+				return;
+			}
+
+			uploadError( error.file, error.code, error.message, up );
 			up.refresh();
 		});
 
-		uploader.bind('FileUploaded', function(up, file, response) {
-			uploadSuccess(file, response.response);
+		uploader.bind( 'FileUploaded', function( up, file, response ) {
+			uploadSuccess( file, response.response );
 		});
 
-		uploader.bind('UploadComplete', function() {
+		uploader.bind( 'UploadComplete', function() {
 			uploadComplete();
 		});
+
+		/**
+		 * When uploading images add a file reference used to retrieve the attachment_id
+		 * if the uploading fails due to a server timeout of out of memoty error (HTTP 500 errors).
+		 *
+		 * @param {plupload.Uploader} up   Uploader instance.
+		 * @param {plupload.File}     file File for uploading.
+		 */
+		uploader.bind( 'BeforeUpload', function( up, file ) {
+			if ( file.type && file.type.indexOf( 'image/' ) === 0 ) {
+				up.settings.multipart_params._wp_temp_image_ref = file.id;
+			} else {
+				unset( up.settings.multipart_params._wp_temp_image_ref );
+			}
+		} );
 	};
 
-	if ( typeof(wpUploaderInit) == 'object' ) {
+	if ( typeof( wpUploaderInit ) == 'object' ) {
 		uploader_init();
 	}
 
Index: src/js/_enqueues/vendor/plupload/wp-plupload.js
===================================================================
--- src/js/_enqueues/vendor/plupload/wp-plupload.js	(revision 45788)
+++ src/js/_enqueues/vendor/plupload/wp-plupload.js	(working copy)
@@ -33,13 +33,17 @@
 	 */
 	Uploader = function( options ) {
 		var self = this,
-			isIE = navigator.userAgent.indexOf('Trident/') != -1 || navigator.userAgent.indexOf('MSIE ') != -1,
+			isIE, // not used, back-compat
 			elements = {
 				container: 'container',
 				browser:   'browse_button',
 				dropzone:  'drop_element'
 			},
-			key, error;
+			tryAgainCount = {},
+			tryAgain,
+			key,
+			error,
+			fileUploaded;
 
 		this.supports = {
 			upload: Uploader.browser.supported
@@ -95,14 +99,6 @@
 			return;
 		}
 
-		// Make sure flash sends cookies (seems in IE it does without switching to urlstream mode)
-		if ( ! isIE && 'flash' === plupload.predictRuntime( this.plupload ) &&
-			( ! this.plupload.required_features || ! this.plupload.required_features.hasOwnProperty( 'send_binary_string' ) ) ) {
-
-			this.plupload.required_features = this.plupload.required_features || {};
-			this.plupload.required_features.send_binary_string = true;
-		}
-
 		// Initialize the plupload instance.
 		this.uploader = new plupload.Uploader( this.plupload );
 		delete this.plupload;
@@ -112,16 +108,98 @@
 		delete this.params;
 
 		/**
+		 * Attempt to create image sub-sizes when an image was uploaded successfully
+		 * but the server responded with HTTP 500 error.
+		 *
+		 * @since 5.3.0
+		 *
+		 * @param  {string}        message  Error message.
+		 * @param  {object}        data     Error data from Plupload.
+		 * @param  {plupload.File} file     File that was uploaded.
+		 */
+		tryAgain = function( message, data, file ) {
+			var times;
+
+			if ( ! file || ! file.id ) {
+				error( message, data, file, false );
+				return;
+			}
+
+			times = tryAgainCount[ file.id ];
+
+			if ( times && times > 3 ) {
+				error( message, data, file, false );
+				return;
+			}
+
+			if ( ! times ) {
+				tryAgainCount[ file.id ] = 1;
+			} else {
+				tryAgainCount[ file.id ] = ++times;
+			}
+
+			// Another request to try to create the missing image sub-sizes.
+			$.ajax({
+				type: 'post',
+				url: ajaxurl,
+				dataType: 'json',
+				data: {
+					action: 'media-create-image-subsizes',
+					_wpnonce: _wpPluploadSettings.defaults.multipart_params._wpnonce,
+					_wp_temp_image_ref: file.id, // Used to find the new attachment_id.
+				}
+			}).done( function( response ) {
+				var newMessage;
+
+				if ( response.success ) {
+					fileUploaded( self.uploader, file, response );
+				} else {
+					if ( response.data && response.data.message ) {
+						newMessage = response.data.message;
+					} else if ( _.isString( response ) ) {
+						// Can be error message coming from PHP that has few simple HTML tags. Remove them.
+						newMessage = response.replace( /<\/?[a-zA-Z][^>]*>/g, '' );
+						newMessage = _.escape( newMessage );
+					}
+
+					if ( ! newMessage ) {
+						newMessage = message;
+					}
+
+					error( newMessage, data, file, false );
+				}
+			}).fail( function( jqXHR ) {
+				// If another HTTP 500 error, try again up to 3 times.
+				if ( jqXHR.status === 500 ) {
+					tryAgain( message, data, file );
+					return;
+				}
+
+				error( message, data, file, false );
+			});
+		}
+
+		/**
 		 * Custom error callback.
 		 *
 		 * Add a new error to the errors collection, so other modules can track
 		 * and display errors. @see wp.Uploader.errors.
 		 *
-		 * @param  {string}        message
-		 * @param  {object}        data
+		 * @param  {string}        message  Error message.
+		 * @param  {object}        data     Error data from Plupload.
 		 * @param  {plupload.File} file     File that was uploaded.
+		 * @param  {boolean}       retry    Whether to try again to create image sub-sizes.
 		 */
-		error = function( message, data, file ) {
+		error = function( message, data, file, retry ) {
+			var isImage = file.type && file.type.indexOf( 'image/' ) === 0;
+			var status  = data && data.status;
+
+			// If the file is an image and the error is HTTP 500 try to create sub-sizes again.
+			if ( retry !== false && status === 500 && isImage ) {
+				tryAgain( message, data, file );
+				return;
+			}
+
 			if ( file.attachment ) {
 				file.attachment.destroy();
 			}
@@ -136,6 +214,36 @@
 		};
 
 		/**
+		 * After a file is successfully uploaded, update its model.
+		 *
+		 * @param {plupload.Uploader} up       Uploader instance.
+		 * @param {plupload.File}     file     File that was uploaded.
+		 * @param {Object}            response Object with response properties.
+		 */
+		fileUploaded = function( up, file, response ) {
+			var complete;
+
+			// Remove the "uploading" UI elements
+			_.each( ['file','loaded','size','percent'], function( key ) {
+				file.attachment.unset( key );
+			} );
+
+			file.attachment.set( _.extend( response.data, { uploading: false } ) );
+
+			wp.media.model.Attachment.get( response.data.id, file.attachment );
+
+			complete = Uploader.queue.all( function( attachment ) {
+				return ! attachment.get('uploading');
+			});
+
+			if ( complete ) {
+				Uploader.queue.reset();
+			}
+
+			self.success( file.attachment );
+		}
+
+		/**
 		 * After the Uploader has been initialized, initialize some behaviors for the dropzone.
 		 *
 		 * @param {plupload.Uploader} uploader Uploader instance.
@@ -203,10 +311,25 @@
 		}
 
 		/**
+		 * When uploading images add a file reference used to retrieve the attachment_id
+		 * if the uploading fails due to a server timeout of out of memoty (HTTP 500) error.
+		 *
+		 * @param {plupload.Uploader} up   Uploader instance.
+		 * @param {plupload.File}     file File for uploading.
+		 */
+		this.uploader.bind( 'BeforeUpload', function( up, file ) {
+			if ( file.type && file.type.indexOf( 'image/' ) === 0 ) {
+				up.settings.multipart_params._wp_temp_image_ref = file.id;
+			} else {
+				unset( up.settings.multipart_params._wp_temp_image_ref );
+			}
+		} );
+
+		/**
 		 * After files were filtered and added to the queue, create a model for each.
 		 *
-		 * @param {plupload.Uploader} uploader Uploader instance.
-		 * @param {Array}             files    Array of file objects that were added to queue by the user.
+		 * @param {plupload.Uploader} up    Uploader instance.
+		 * @param {Array}             files Array of file objects that were added to queue by the user.
 		 */
 		this.uploader.bind( 'FilesAdded', function( up, files ) {
 			_.each( files, function( file ) {
@@ -259,13 +382,12 @@
 		/**
 		 * After a file is successfully uploaded, update its model.
 		 *
-		 * @param {plupload.Uploader} uploader Uploader instance.
+		 * @param {plupload.Uploader} up       Uploader instance.
 		 * @param {plupload.File}     file     File that was uploaded.
 		 * @param {Object}            response Object with response properties.
 		 * @return {mixed}
 		 */
 		this.uploader.bind( 'FileUploaded', function( up, file, response ) {
-			var complete;
 
 			try {
 				response = JSON.parse( response.response );
@@ -273,33 +395,21 @@
 				return error( pluploadL10n.default_error, e, file );
 			}
 
-			if ( ! _.isObject( response ) || _.isUndefined( response.success ) )
+			if ( ! _.isObject( response ) || _.isUndefined( response.success ) ) {
 				return error( pluploadL10n.default_error, null, file );
-			else if ( ! response.success )
+			} else if ( ! response.success ) {
 				return error( response.data && response.data.message, response.data, file );
+			}
 
-			_.each(['file','loaded','size','percent'], function( key ) {
-				file.attachment.unset( key );
-			});
-
-			file.attachment.set( _.extend( response.data, { uploading: false }) );
-			wp.media.model.Attachment.get( response.data.id, file.attachment );
-
-			complete = Uploader.queue.all( function( attachment ) {
-				return ! attachment.get('uploading');
-			});
-
-			if ( complete )
-				Uploader.queue.reset();
-
-			self.success( file.attachment );
+			// Success. Update the UI with the new attachment.
+			fileUploaded( up, file, response );
 		});
 
 		/**
 		 * When plupload surfaces an error, send it to the error handler.
 		 *
-		 * @param {plupload.Uploader} uploader Uploader instance.
-		 * @param {Object}            error    Contains code, message and sometimes file and other details.
+		 * @param {plupload.Uploader} up            Uploader instance.
+		 * @param {Object}            pluploadError Contains code, message and sometimes file and other details.
 		 */
 		this.uploader.bind( 'Error', function( up, pluploadError ) {
 			var message = pluploadL10n.default_error,
@@ -338,11 +448,14 @@
 		'IMAGE_DIMENSIONS_ERROR': pluploadL10n.image_dimensions_exceeded,
 		'GENERIC_ERROR':          pluploadL10n.upload_failed,
 		'IO_ERROR':               pluploadL10n.io_error,
-		'HTTP_ERROR':             pluploadL10n.http_error,
 		'SECURITY_ERROR':         pluploadL10n.security_error,
 
 		'FILE_SIZE_ERROR': function( file ) {
 			return pluploadL10n.file_exceeds_size_limit.replace('%s', file.name);
+		},
+
+		'HTTP_ERROR': function( file, pluploadError ) {
+			return pluploadError.response || pluploadL10n.http_error;
 		}
 	};
 
Index: src/js/media/views/uploader/status.js
===================================================================
--- src/js/media/views/uploader/status.js	(revision 45788)
+++ src/js/media/views/uploader/status.js	(working copy)
@@ -111,10 +111,13 @@
 	 * @param {Backbone.Model} error
 	 */
 	error: function( error ) {
-		this.views.add( '.upload-errors', new wp.media.view.UploaderStatusError({
-			filename: this.filename( error.get('file').name ),
-			message:  error.get('message')
-		}), { at: 0 });
+		var statusError = new wp.media.view.UploaderStatusError( {
+			filename: this.filename( error.get( 'file' ).name ),
+			message:  error.get( 'message' )
+		} );
+
+		// TBD: perhaps show additional info here while retrying to create image sub-sizes?
+		this.views.add( '.upload-errors', statusError, { at: 0 } );
 	},
 
 	dismiss: function() {
Index: src/wp-admin/admin-ajax.php
===================================================================
--- src/wp-admin/admin-ajax.php	(revision 45788)
+++ src/wp-admin/admin-ajax.php	(working copy)
@@ -105,6 +105,7 @@
 	'send-link-to-editor',
 	'send-attachment-to-editor',
 	'save-attachment-order',
+	'media-create-image-subsizes',
 	'heartbeat',
 	'get-revision-diffs',
 	'save-user-color-scheme',
Index: src/wp-admin/includes/ajax-actions.php
===================================================================
--- src/wp-admin/includes/ajax-actions.php	(revision 45788)
+++ src/wp-admin/includes/ajax-actions.php	(working copy)
@@ -2317,6 +2317,59 @@
 }
 
 /**
+ * Ajax handler for creating missing image sub-sizes for just uploaded images.
+ *
+ * @since 5.3.0
+ */
+function wp_ajax_media_create_image_subsizes() {
+	check_ajax_referer( 'media-form' );
+
+	if ( ! current_user_can( 'upload_files' ) ) {
+		wp_send_json_error( array( 'message' => __( 'Sorry, you are not allowed to upload files.' ) ) );
+	}
+
+	// Using Plupload `file.id` as ref.
+	if ( ! empty( $_POST['_wp_temp_image_ref'] ) ) {
+		$image_ref = preg_replace( '/[^a-zA-Z0-9_]/', '', $_POST['_wp_temp_image_ref'] );
+	} else {
+		wp_send_json_error( array( 'message' => __( 'Invalid file reference.' ) ) );
+	}
+
+	// Uploading of images usually fails while creating the sub-sizes, either because of a timeout or out of memory.
+	// At this point the file has been uploaded and an attachment post created, but because of the PHP fatal error
+	// the cliend doesn't know the attachment ID yet.
+	// To be able to find the new attachment_id in these cases we temporarily store an upload reference sent by the client
+	// in the original upload request. It is used to save a transient with the attachment_id as value.
+	// That reference currently is Plupload's `file.id` but can be any sufficiently random alpha-numeric string.
+	$attachment_id = get_transient( '_wp_temp_image_ref:' . $image_ref );
+
+	if ( empty( $attachment_id ) ) {
+		wp_send_json_error( array( 'message' => __( 'Upload failed. Please reload and try again.' ) ) );
+	}
+
+	// This can still be pretty slow and cause timeout or out of memory errors.
+	// The js that handles the response would need to also handle HTTP 500 errors.
+	wp_update_image_subsizes( $attachment_id );
+
+	if ( ! empty( $_POST['_legasy_support'] ) ) {
+		// The old (inline) uploader. Only needs the attachment_id.
+		$response = array( 'id' => $attachment_id );
+	} else {
+		// Media modal and Media Library grid view.
+		$response = wp_prepare_attachment_for_js( $attachment_id );
+
+		if ( ! $response ) {
+			wp_send_json_error( array( 'message' => __( 'Upload failed.' ) ) );
+		}
+	}
+
+	// At this point the image has been uploaded successfully.
+	delete_transient( '_wp_temp_image_ref:' . $image_ref );
+
+	wp_send_json_success( $response );
+}
+
+/**
  * Ajax handler for uploading attachments
  *
  * @since 3.3.0
Index: src/wp-admin/includes/media.php
===================================================================
--- src/wp-admin/includes/media.php	(revision 45788)
+++ src/wp-admin/includes/media.php	(working copy)
@@ -288,6 +288,7 @@
 
 	$time = current_time( 'mysql' );
 	$post = get_post( $post_id );
+
 	if ( $post ) {
 		// The post date doesn't usually matter for pages, so don't backdate this upload.
 		if ( 'page' !== $post->post_type && substr( $post->post_date, 0, 4 ) > 0 ) {
@@ -305,12 +306,13 @@
 	$ext  = pathinfo( $name, PATHINFO_EXTENSION );
 	$name = wp_basename( $name, ".$ext" );
 
-	$url     = $file['url'];
-	$type    = $file['type'];
-	$file    = $file['file'];
-	$title   = sanitize_text_field( $name );
-	$content = '';
-	$excerpt = '';
+	$url       = $file['url'];
+	$type      = $file['type'];
+	$file      = $file['file'];
+	$title     = sanitize_text_field( $name );
+	$content   = '';
+	$excerpt   = '';
+	$image_ref = false;
 
 	if ( preg_match( '#^audio#', $type ) ) {
 		$meta = wp_read_audio_metadata( $file );
@@ -370,8 +372,14 @@
 		}
 
 		// Use image exif/iptc data for title and caption defaults if possible.
-	} elseif ( 0 === strpos( $type, 'image/' ) ) {
+	} elseif ( strpos( $type, 'image/' ) === 0 ) {
+		// Image file reference passed by the uploader.
+		if ( ! empty( $_POST['_wp_temp_image_ref'] ) ) {
+			$image_ref = preg_replace( '/[^a-zA-Z0-9_]/', '', $_POST['_wp_temp_image_ref'] );
+		}
+
 		$image_meta = wp_read_image_metadata( $file );
+
 		if ( $image_meta ) {
 			if ( trim( $image_meta['title'] ) && ! is_numeric( sanitize_title( $image_meta['title'] ) ) ) {
 				$title = $image_meta['title'];
@@ -400,13 +408,26 @@
 	unset( $attachment['ID'] );
 
 	// Save the data
-	$id = wp_insert_attachment( $attachment, $file, $post_id, true );
-	if ( ! is_wp_error( $id ) ) {
-		wp_update_attachment_metadata( $id, wp_generate_attachment_metadata( $id, $file ) );
+	$attachment_id = wp_insert_attachment( $attachment, $file, $post_id, true );
+
+	if ( ! is_wp_error( $attachment_id ) ) {
+		// If an image, keep the upload reference until all image sub-sizes are created.
+		if ( $image_ref ) {
+			set_transient( '_wp_temp_image_ref:' . $image_ref, $attachment_id, 6 * HOUR_IN_SECONDS );
+		}
+
+		// The image sub-sizes are created during wp_generate_attachment_metadata().
+		// This is generally slow and may cause timeouts or out of memory errors.
+		wp_update_attachment_metadata( $attachment_id, wp_generate_attachment_metadata( $attachment_id, $file ) );
+
+		// At this point the image is uploaded successfully even if there were specific errors or some sub-sizes were not created.
+		// The transient is not needed any more.
+		if ( $image_ref ) {
+			delete_transient( '_wp_temp_image_ref:' . $image_ref );
+		}
 	}
 
-	return $id;
-
+	return $attachment_id;
 }
 
 /**
Index: src/wp-includes/script-loader.php
===================================================================
--- src/wp-includes/script-loader.php	(revision 45788)
+++ src/wp-includes/script-loader.php	(working copy)
@@ -1124,7 +1124,7 @@
 		'default_error'             => __( 'An error occurred in the upload. Please try again later.' ),
 		'missing_upload_url'        => __( 'There was a configuration error. Please contact the server administrator.' ),
 		'upload_limit_exceeded'     => __( 'You may only upload 1 file.' ),
-		'http_error'                => __( 'HTTP error.' ),
+		'http_error'                => __( 'Unexpected response from the server. The file may have been uploaded successfully. Please check in the Media Library or reload the page.' ),
 		'upload_failed'             => __( 'Upload failed.' ),
 		/* translators: 1: Opening link tag, 2: Closing link tag */
 		'big_upload_failed'         => __( 'Please try uploading this file with the %1$sbrowser uploader%2$s.' ),