Implement the gamepad API in the IPC proxy

ppapi/proxy/gamepad_resource.h

Index: ppapi/proxy/gamepad_resource.h
diff --git a/ppapi/proxy/gamepad_resource.h b/ppapi/proxy/gamepad_resource.h
index 61d66b0c4451592c19fc3a77166e52d273692a00..5a19203f59c116fe86313bea0cf1a6a15237fb59 100644
--- a/ppapi/proxy/gamepad_resource.h
+++ b/ppapi/proxy/gamepad_resource.h
@@ -9,8 +9,10 @@
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/shared_memory.h"
+#include "ppapi/c/ppb_gamepad.h"
 #include "ppapi/proxy/plugin_resource.h"
 #include "ppapi/proxy/ppapi_proxy_export.h"
+#include "ppapi/shared_impl/ppb_gamepad_shared.h"
 #include "ppapi/thunk/ppb_gamepad_api.h"
 
 struct PP_GamepadsSampleData;
@@ -45,7 +47,10 @@ class PPAPI_PROXY_EXPORT GamepadResource
                              base::SharedMemoryHandle shared_memory_handle);
 
   scoped_ptr<base::SharedMemory> shared_memory_;
-  void* buffer_;
+  const ContentGamepadHardwareBuffer* buffer_;
+
+  // Last data returned so we can use this in the event of a read failure.
+  PP_GamepadsSampleData last_read_;
 
   DISALLOW_COPY_AND_ASSIGN(GamepadResource);
 };