Index: src/wp-includes/css/editor.css
===================================================================
--- src/wp-includes/css/editor.css	(revision 28575)
+++ src/wp-includes/css/editor.css	(working copy)
@@ -1782,6 +1782,17 @@
 	height: 30px;
 }
 
+/* Resize helper. */
+
+.mce-resize-helper {
+	background-color: rgba( 0, 0, 0, 0.75 );
+	border-radius: 3px;
+	color: white;
+	margin: 5px;
+	padding: 5px;
+	position: absolute;
+}
+
 @media screen and ( max-width: 782px ) {
 	#wp-fullscreen-close,
 	#wp-fullscreen-central-toolbar,
Index: src/wp-includes/js/tinymce/plugins/wpeditimage/plugin.js
===================================================================
--- src/wp-includes/js/tinymce/plugins/wpeditimage/plugin.js	(revision 28575)
+++ src/wp-includes/js/tinymce/plugins/wpeditimage/plugin.js	(working copy)
@@ -963,6 +963,30 @@
 		}
 	});
 
+	// Resize helper.
+
+	editor.on( 'init', function() {
+		var ghostObject, iFramePos, resizeHelper;
+
+		editor.on( 'ObjectResizeStart', function( event ) {
+			resizeHelper = tinymce.DOM.create( 'DIV', { 'class': 'mce-resize-helper' }, event.width + ' × ' + event.height );
+			ghostObject = editor.dom.select( '.mce-clonedresizable' )[0];
+			iFramePos = tinymce.DOM.getPos( editor.getContentAreaContainer().querySelector( 'iframe' ) );
+			document.body.appendChild( resizeHelper );
+			editor.on( 'mousemove', resizing );
+		} );
+
+		editor.on( 'ObjectResized', function() {
+			editor.off( 'mousemove', resizing );
+			tinymce.DOM.remove( resizeHelper );
+		} );
+
+		function resizing( event ) {
+			tinymce.DOM.setStyles( resizeHelper, { 'top': event.clientY + iFramePos.y, 'left': event.clientX + iFramePos.x } );
+			tinymce.DOM.setHTML( resizeHelper, ghostObject.width + ' × ' + ghostObject.height );
+		}
+	} );
+
 	return {
 		_do_shcode: parseShortcode,
 		_get_shcode: getShortcode