Support buttons attribute for drag event (chromium side).

content/shell/renderer/test_runner/event_sender.h

 // Copyright 2014 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 CONTENT_SHELL_RENDERER_TEST_RUNNER_EVENT_SENDER_H_
 #define CONTENT_SHELL_RENDERER_TEST_RUNNER_EVENT_SENDER_H_
 
 #include <queue>
 #include <string>
 #include <vector>
@@ skipping 237 matching lines @@
 
   scoped_ptr<blink::WebContextMenuData> last_context_menu_data_;
 
   blink::WebDragData current_drag_data_;
 
   // Location of the touch point that initiated a gesture.
   blink::WebPoint current_gesture_location_;
 
   // Currently pressed mouse button (Left/Right/Middle or None).
   static blink::WebMouseEvent::Button pressed_button_;
+  static int modifiers_;
 
   bool replaying_saved_events_;
 
   std::deque<SavedEvent> mouse_event_queue_;
 
   blink::WebDragOperationsMask current_drag_effects_allowed_;
 
   // Location of last mouseMoveTo event.
   static blink::WebPoint last_mouse_pos_;
 
@@ skipping 11 matching lines @@
   int click_count_;
 
   base::WeakPtrFactory<EventSender> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(EventSender);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_SHELL_RENDERER_TEST_RUNNER_EVENT_SENDER_H_