Convert resources to take an instance key instead of an Instance*.

ppapi/cpp/dev/widget_client_dev.h

 // Copyright (c) 2010 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_CLIENT_DEV_H_
 #define PPAPI_CPP_DEV_WIDGET_CLIENT_DEV_H_
 
 #include "ppapi/c/pp_stdint.h"
+#include "ppapi/cpp/instance_handle.h"
 
 namespace pp {
 
-class Instance;
 class Rect;
 class Scrollbar_Dev;
 class Widget_Dev;
 
 // This class provides a C++ interface for callbacks related to widgets. You
 // would normally use multiple inheritance to derive from this class in your
 // instance.
 class WidgetClient_Dev {
  public:
-  WidgetClient_Dev(Instance* instance);
+  explicit WidgetClient_Dev(const InstanceHandle& instance);
   virtual ~WidgetClient_Dev();
 
   /**
    * Notification that the given widget should be repainted. This is the
    * implementation for PPP_Widget_Dev.
    */
   virtual void InvalidateWidget(Widget_Dev widget, const Rect& dirty_rect) = 0;
 
   /**
    * Notification that the given scrollbar should change value. This is the
    * implementation for PPP_Scrollbar_Dev.
    */
   virtual void ScrollbarValueChanged(Scrollbar_Dev scrollbar,
                                      uint32_t value) = 0;
 
   /**
    * Notification that the given scrollbar's overlay type has changed. This is
    * the implementation for PPP_Scrollbar_Dev.
    */
   virtual void ScrollbarOverlayChanged(Scrollbar_Dev scrollbar,
                                        bool type) = 0;
 
  private:
-  Instance* associated_instance_;
+  InstanceHandle associated_instance_;
 };
 
 }  // namespace pp
 
 #endif  // PPAPI_CPP_DEV_WIDGET_CLIENT_DEV_H_