ui: Cleanup class/struct forward declarations

ui/platform_window/platform_window.h

 // Copyright 2014 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_PLATFORM_WINDOW_PLATFORM_WINDOW_H_
 #define UI_PLATFORM_WINDOW_PLATFORM_WINDOW_H_
 
 #include <memory>
 
 #include "base/strings/string16.h"
 #include "ui/base/cursor/cursor.h"
 
 namespace gfx {
 class Rect;
 }
 
 namespace ui {
 
 class PlatformImeController;
-class PlatformWindowDelegate;
 
 // Platform window.
 //
 // Each instance of PlatformWindow represents a single window in the
 // underlying platform windowing system (i.e. X11/Win/OSX).
 class PlatformWindow {
  public:
   virtual ~PlatformWindow() {}
 
   virtual void Show() = 0;
@@ skipping 25 matching lines @@
   virtual void ConfineCursorToBounds(const gfx::Rect& bounds) = 0;
 
   // The PlatformImeController is owned by the PlatformWindow, the ownership is
   // not transferred.
   virtual PlatformImeController* GetPlatformImeController() = 0;
 };
 
 }  // namespace ui
 
 #endif  // UI_PLATFORM_WINDOW_PLATFORM_WINDOW_H_