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

ui/wm/core/wm_state.h

 // 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.
 
 #ifndef UI_WM_CORE_WM_STATE_H_
 #define UI_WM_CORE_WM_STATE_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "ui/wm/wm_export.h"
 
-namespace ui {
-class PlatformEventSource;
-}
-
 namespace wm {
 
 class TransientWindowController;
 class TransientWindowStackingClient;
 
 // Installs state needed by the window manager.
 class WM_EXPORT WMState {
  public:
   WMState();
   ~WMState();
 
   // WindowStackingClient:
  private:
   scoped_ptr<TransientWindowStackingClient> window_stacking_client_;
   scoped_ptr<TransientWindowController> transient_window_client_;
-  scoped_ptr<ui::PlatformEventSource> event_source_;
 
   DISALLOW_COPY_AND_ASSIGN(WMState);
 };
 
 }  // namespace wm
 
 #endif  // UI_WM_CORE_WM_STATE_H_