Implement WebContentsView::GetDropData for Mac; disable on Aura

chrome/browser/resources/extensions/extensions.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 <include src="../shared/js/cr/ui/drag_wrapper.js"></include>
 <include src="../uber/uber_utils.js"></include>
 <include src="extension_list.js"></include>
 <include src="pack_extension_overlay.js"></include>
 
 // Used for observing function of the backend datasource for this page by
@@ skipping 76 matching lines @@
 
       // Set up the three dev mode buttons (load unpacked, pack and update).
       $('load-unpacked').addEventListener('click',
           this.handleLoadUnpackedExtension_.bind(this));
       $('pack-extension').addEventListener('click',
           this.handlePackExtension_.bind(this));
       $('update-extensions-now').addEventListener('click',
           this.handleUpdateExtensionNow_.bind(this));
 
       if (!loadTimeData.getBoolean('offStoreInstallEnabled')) {
-        this.dragWrapper_ =
-            new cr.ui.DragWrapper(document.body, dragWrapperHandler);
+        this.dragWrapper_ = new cr.ui.DragWrapper(document.documentElement,
+                                                  dragWrapperHandler);
       }
 
       var packExtensionOverlay = extensions.PackExtensionOverlay.getInstance();
       packExtensionOverlay.initializePage();
 
       cr.ui.overlay.setupOverlay($('dropTargetOverlay'));
     },
 
     /**
      * Handles the Load Unpacked Extension button.
@@ skipping 180 matching lines @@
   return {
     ExtensionSettings: ExtensionSettings
   };
 });
 
 var ExtensionSettings = extensions.ExtensionSettings;
 
 window.addEventListener('load', function(e) {
   ExtensionSettings.getInstance().initialize();
 });