Introduce EventProcessor::OnEventProcessingStarted()

ui/aura/window_event_dispatcher.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 UI_AURA_WINDOW_EVENT_DISPATCHER_H_
 #define UI_AURA_WINDOW_EVENT_DISPATCHER_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 157 matching lines @@
   Window* GetGestureTarget(ui::GestureEvent* event);
 
   // Overridden from aura::client::CaptureDelegate:
   virtual void UpdateCapture(Window* old_capture, Window* new_capture) OVERRIDE;
   virtual void OnOtherRootGotCapture() OVERRIDE;
   virtual void SetNativeCapture() OVERRIDE;
   virtual void ReleaseNativeCapture() OVERRIDE;
 
   // Overridden from ui::EventProcessor:
   virtual ui::EventTarget* GetRootTarget() OVERRIDE;
-  virtual void PrepareEventForDispatch(ui::Event* event) OVERRIDE;
+  virtual bool OnEventProcessingStarted(ui::Event* event) OVERRIDE;
 
   // Overridden from ui::EventDispatcherDelegate.
   virtual bool CanDispatchToTarget(ui::EventTarget* target) OVERRIDE;
   virtual ui::EventDispatchDetails PreDispatchEvent(ui::EventTarget* target,
                                                     ui::Event* event) OVERRIDE;
   virtual ui::EventDispatchDetails PostDispatchEvent(
       ui::EventTarget* target, const ui::Event& event) OVERRIDE;
 
   // Overridden from ui::GestureEventHelper.
   virtual bool CanDispatchToConsumer(ui::GestureConsumer* consumer) OVERRIDE;
@@ skipping 74 matching lines @@
 
   // Used to schedule DispatchHeldEvents() when |move_hold_count_| goes to 0.
   base::WeakPtrFactory<WindowEventDispatcher> held_event_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowEventDispatcher);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_WINDOW_EVENT_DISPATCHER_H_