Index: src/wp-includes/js/tinymce/plugins/wordpress/plugin.js
===================================================================
--- src/wp-includes/js/tinymce/plugins/wordpress/plugin.js	(revision 27092)
+++ src/wp-includes/js/tinymce/plugins/wordpress/plugin.js	(working copy)
@@ -278,7 +278,7 @@
 	editor.on( 'init', function() {
 		var env = tinymce.Env,
 			bodyClass = ['mceContentBody'], // back-compat for themes that use this in editor-style.css...
-			body = editor.getBody();
+			doc = editor.getDoc();
 
 		if ( editor.getParam( 'directionality' ) === 'rtl' ) {
 			bodyClass.push('rtl');
@@ -298,7 +298,7 @@
 
 		tinymce.each( bodyClass, function( cls ) {
 			if ( cls ) {
-				editor.dom.addClass( body, cls );
+				editor.dom.addClass( doc.body, cls );
 			}
 		});
 
@@ -314,6 +314,44 @@
 		if ( typeof window.jQuery !== 'undefined' ) {
 			window.jQuery( document ).triggerHandler( 'tinymce-editor-init', [editor] );
 		}
+
+		// When scrolling with mouse wheel or trackpad inside the editor, don't scroll the parent window
+		editor.dom.bind( doc, 'onwheel' in doc ? 'wheel' : 'mousewheel', function( event ) {
+			var delta, docElement = doc.documentElement;
+
+			if ( editor.settings.wp_fullscreen || 'ontouchstart' in window ) {
+				return;
+			}
+
+			if ( typeof event.deltaY !== 'undefined' ) {
+				delta = event.deltaY;
+
+				if ( typeof event.deltaMode !== 'undefined' && event.deltaMode === event.DOM_DELTA_LINE ) {
+					delta *= 20;
+				}
+			} else {
+				delta = -event.wheelDelta;
+			}
+
+			// Reverse direction for MacOS
+			if ( env.mac ) {
+				delta *= -1;
+			}
+
+			event.preventDefault();
+
+			if ( ( docElement.scrollTop === 0 && delta < 0 ) ||
+				( docElement.clientHeight + docElement.scrollTop === docElement.scrollHeight && delta > 0 ) ) {
+
+				return;
+			}
+
+			if ( env.webkit ) {
+				doc.body.scrollTop += delta;
+			} else {
+				docElement.scrollTop += delta;
+			}
+		});
 	});
 
 	// Word count