events: Move the PlatformEventSource creation in aura::Env.

ui/wm/core/wm_state.cc

 // Copyright (c) 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.
 
 #include "ui/wm/core/wm_state.h"
 
 #include "ui/events/platform/platform_event_source.h"
 #include "ui/wm/core/transient_window_controller.h"
 #include "ui/wm/core/transient_window_stacking_client.h"
 
 namespace wm {
 
 WMState::WMState()
     : window_stacking_client_(new TransientWindowStackingClient),
       transient_window_client_(new TransientWindowController) {
   aura::client::SetWindowStackingClient(window_stacking_client_.get());
   aura::client::SetTransientWindowClient(transient_window_client_.get());
-  if (!ui::PlatformEventSource::GetInstance())
-    event_source_ = ui::PlatformEventSource::CreateDefault();
 }
 
 WMState::~WMState() {
   if (aura::client::GetWindowStackingClient() == window_stacking_client_.get())
     aura::client::SetWindowStackingClient(NULL);
 
   if (aura::client::GetTransientWindowClient() ==
       transient_window_client_.get()) {
     aura::client::SetTransientWindowClient(NULL);
   }
 }
 
 }  // namespace wm