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

ppapi/cpp/private/flash_fullscreen.h

Index: ppapi/cpp/private/flash_fullscreen.h
diff --git a/ppapi/cpp/private/flash_fullscreen.h b/ppapi/cpp/private/flash_fullscreen.h
index 539f249ee02328a2e618e8cee52bb895873479fb..224824dc131d0685af44bac94c5020e753411f27 100644
--- a/ppapi/cpp/private/flash_fullscreen.h
+++ b/ppapi/cpp/private/flash_fullscreen.h
@@ -5,14 +5,15 @@
 #ifndef PPAPI_CPP_PRIVATE_FLASH_FULLSCREEN_H_
 #define PPAPI_CPP_PRIVATE_FLASH_FULLSCREEN_H_
 
+#include "ppapi/cpp/instance_handle.h"
+
 namespace pp {
 
-class Instance;
 class Size;
 
 class FlashFullscreen {
  public:
-  FlashFullscreen(Instance* instance);
+  FlashFullscreen(const InstanceHandle& instance);
   virtual ~FlashFullscreen();
 
   // PPB_FlashFullscreen methods.
@@ -21,7 +22,7 @@ class FlashFullscreen {
   bool GetScreenSize(Size* size);
 
  private:
-  Instance* instance_;
+  InstanceHandle instance_;
 };
 
 }  // namespace pp