Make the cancelling of drag and drop match Safari for Windows.

webkit/glue/webview.h

 // Copyright (c) 2009 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.
 
 #ifndef WEBKIT_GLUE_WEBVIEW_H_
 #define WEBKIT_GLUE_WEBVIEW_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 153 matching lines @@
   // WebView (if there is such an image)
   virtual void CopyImageAt(int x, int y) = 0;
 
   // Inspect a particular point in the WebView. (x = -1 || y = -1) is a special
   // case which means inspect the current page and not a specific point.
   virtual void InspectElement(int x, int y) = 0;
 
   // Show the JavaScript console.
   virtual void ShowJavaScriptConsole() = 0;
 
+  // Notifies the webview that a drag has been cancelled.
+  virtual void DragSourceCancelledAt(
+      const WebKit::WebPoint& client_point,
+      const WebKit::WebPoint& screen_point) = 0;
+
   // Notifies the webview that a drag has terminated.
   virtual void DragSourceEndedAt(
       const WebKit::WebPoint& client_point,
       const WebKit::WebPoint& screen_point) = 0;
 
   // Notifies the webview that a drag and drop operation is in progress, with
   // dropable items over the view.
   virtual void DragSourceMovedTo(
       const WebKit::WebPoint& client_point,
       const WebKit::WebPoint& screen_point) = 0;
@@ skipping 39 matching lines @@
   // Makes the webview transparent. Useful if you want to have some custom
   // background behind it.
   virtual void SetIsTransparent(bool is_transparent) = 0;
   virtual bool GetIsTransparent() const = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(WebView);
 };
 
 #endif  // WEBKIT_GLUE_WEBVIEW_H_