Forward mouse down node information to WebWidgetClient

public/web/WebWidgetClient.h

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 147 matching lines @@
     // coordinates.
     // |tappedNode| is the node that the mouseDown event hit, provided so the
     // UI can be shown only on certain kinds of nodes in specific locations.
     // |pageChanged| is true if and only if the DOM tree or style was
     // modified during the dispatch of the mouse*, or click events associated
     // with the tap.
     // This provides a heuristic to help identify when a page is doing
     // something as a result of a tap without explicitly consuming the event.
     virtual void showUnhandledTapUIIfNeeded(const WebPoint& tappedPosition,
         const WebNode& tappedNode, bool pageChanged) { }
+
+    // Called immediately after a mousedown event is dispatched due to a mouse
+    // press or gesture tap.
+    // Note: This is called even when the mouse down event is prevent default.
+    virtual void onMouseDown(const WebNode& mouseDownNode) { }
 protected:
     ~WebWidgetClient() { }
 };
 
 } // namespace blink
 
 #endif