Remove stops_event_propagation from Window, since it's broken.

ui/aura/client/event_client.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/aura/client/event_client.h"
 
 #include "ui/aura/root_window.h"
 #include "ui/aura/window_property.h"
 
 DECLARE_WINDOW_PROPERTY_TYPE(aura::client::EventClient*)
 
 namespace aura {
 namespace client {
 
 DEFINE_WINDOW_PROPERTY_KEY(EventClient*, kRootWindowEventClientKey, NULL);
 
 void SetEventClient(RootWindow* root_window, EventClient* client) {
   root_window->SetProperty(kRootWindowEventClientKey, client);
 }
 
 EventClient* GetEventClient(const RootWindow* root_window) {
   return root_window ?
       root_window->GetProperty(kRootWindowEventClientKey) : NULL;
 }
 
 }  // namespace client
 }  // namespace aura