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

ppapi/cpp/fullscreen.h

Index: ppapi/cpp/fullscreen.h
diff --git a/ppapi/cpp/fullscreen.h b/ppapi/cpp/fullscreen.h
index 55922dd78c5a558ae773bc835e9827e64706c2fe..3504424e5a8d249b11203708036bc98be1a8e782 100644
--- a/ppapi/cpp/fullscreen.h
+++ b/ppapi/cpp/fullscreen.h
@@ -5,13 +5,14 @@
 #ifndef PPAPI_CPP_FULLSCREEN_H_
 #define PPAPI_CPP_FULLSCREEN_H_
 
+#include "ppapi/cpp/instance_handle.h"
+
 /// @file
 /// This file defines the API for handling transitions of a module instance to
 /// and from fullscreen mode.
 
 namespace pp {
 
-class Instance;
 class Size;
 
 /// The Fullscreen class allowing you to check and toggle fullscreen mode.
@@ -19,9 +20,9 @@ class Fullscreen {
  public:
   /// A constructor for creating a <code>Fullscreen</code>.
   ///
-  /// @param[in] instance The instance that will own the new
-  /// <code>Fullscreen</code>.
-  Fullscreen(Instance* instance);
+  /// @param[in] instance The instance with which this resource will be
+  /// associated.
+  explicit Fullscreen(const InstanceHandle& instance);
 
   /// Destructor.
   virtual ~Fullscreen();
@@ -63,7 +64,7 @@ class Fullscreen {
   bool GetScreenSize(Size* size);
 
  private:
-  Instance* instance_;
+  InstanceHandle instance_;
 };
 
 }  // namespace pp