aura: Remove event-dispatch methods from WindowTreeHostDelegate interface.

ui/events/event_source.h

 // Copyright 2013 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_EVENTS_EVENT_SOURCE_H_
 #define UI_EVENTS_EVENT_SOURCE_H_
 
+#include "ui/events/event_dispatcher.h"
 #include "ui/events/events_export.h"
 
 namespace ui {
 
 class Event;
 class EventProcessor;
 
 // EventSource receives events from the native platform (e.g. X11, win32 etc.)
 // and sends the events to an EventProcessor.
 class EVENTS_EXPORT EventSource {
  public:
   virtual ~EventSource() {}
 
   virtual EventProcessor* GetEventProcessor() = 0;
 
  protected:
-  void SendEventToProcessor(Event* event);
+  EventDispatchDetails SendEventToProcessor(Event* event);
 };
 
 }  // namespace ui
 
 #endif // UI_EVENTS_EVENT_SOURCE_H_