Cleanup: Remove unneeded forward declarations in ppapi.

ppapi/cpp/dev/widget_dev.h

-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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 PPAPI_CPP_DEV_WIDGET_DEV_H_
 #define PPAPI_CPP_DEV_WIDGET_DEV_H_
 
 #include "ppapi/c/pp_stdint.h"
 #include "ppapi/cpp/resource.h"
 
 namespace pp {
 
 class ImageData;
 class InputEvent;
-class Instance;
 class Rect;
 
 // This is the base class for widget elements.  As such, it can't be created
 // directly.
 class Widget_Dev : public Resource {
  public:
   // Creates an is_null() Widget object.
   Widget_Dev() {}
 
   explicit Widget_Dev(PP_Resource resource);
   Widget_Dev(const Widget_Dev& other);
 
   // PPB_Widget methods:
   bool Paint(const Rect& rect, ImageData* image);
   bool HandleEvent(const InputEvent& event);
   bool GetLocation(Rect* location);
   void SetLocation(const Rect& location);
 };
 
 }  // namespace pp
 
 #endif  // PPAPI_CPP_DEV_WIDGET_DEV_H_