events: Start changing EventHandler interface to not return a value.

ui/base/events/event_dispatcher.cc

 // Copyright (c) 2012 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.
 
 #include "ui/base/events/event_dispatcher.h"
 
 namespace ui {
 
 EventDispatcher::EventDispatcher()
     : set_on_destroy_(NULL),
       current_event_(NULL) {
 }
 
 EventDispatcher::~EventDispatcher() {
   if (set_on_destroy_)
     *set_on_destroy_ = true;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // EventDispatcher, private:
 
-EventResult EventDispatcher::DispatchEventToSingleHandler(EventHandler* handler,
+void EventDispatcher::DispatchEventToSingleHandler(EventHandler* handler,
                                                           Event* event) {
-  return handler->OnEvent(event);
+  handler->OnEvent(event);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // EventDispatcher::ScopedDispatchHelper
 
 EventDispatcher::ScopedDispatchHelper::ScopedDispatchHelper(Event* event)
     : Event::DispatcherApi(event) {
+  set_result(ui::ER_UNHANDLED);
 }
 
 EventDispatcher::ScopedDispatchHelper::~ScopedDispatchHelper() {
   set_phase(EP_POSTDISPATCH);
 }
 
 }  // namespace ui