events: Allow retrieving the current event being dispatched from EventDispatcher.

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) {
+    : set_on_destroy_(NULL),
+      current_event_(NULL) {
 }
 
 EventDispatcher::~EventDispatcher() {
   if (set_on_destroy_)
     *set_on_destroy_ = true;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // EventDispatcher, private:
 
@@ skipping 32 matching lines @@
 
 EventDispatcher::ScopedDispatchHelper::ScopedDispatchHelper(Event* event)
     : Event::DispatcherApi(event) {
 }
 
 EventDispatcher::ScopedDispatchHelper::~ScopedDispatchHelper() {
   set_phase(EP_POSTDISPATCH);
 }
 
 }  // namespace ui