PPAPI: Initialize CompletionCallbackWithOutput storage

ppapi/cpp/private/video_frame_private.h

Index: ppapi/cpp/private/video_frame_private.h
diff --git a/ppapi/cpp/private/video_frame_private.h b/ppapi/cpp/private/video_frame_private.h
index fed9d1da4793c40213a3b0222efd696f9b0b7cd4..7413876e7d648a99e5f94a7b6c82031dbb17ba5c 100644
--- a/ppapi/cpp/private/video_frame_private.h
+++ b/ppapi/cpp/private/video_frame_private.h
@@ -5,6 +5,8 @@
 #ifndef PPAPI_CPP_PRIVATE_VIDEO_FRAME_PRIVATE_H_
 #define PPAPI_CPP_PRIVATE_VIDEO_FRAME_PRIVATE_H_
 
+#include <string.h>
+
 #include "ppapi/c/pp_time.h"
 #include "ppapi/c/private/pp_video_frame_private.h"
 #include "ppapi/cpp/completion_callback.h"
@@ -87,6 +89,11 @@ struct CallbackOutputTraits<pp::VideoFrame_Private> {
   static inline pp::VideoFrame_Private StorageToPluginArg(StorageType& t) {
     return pp::VideoFrame_Private(PASS_REF, t);
   }
+
+  static inline void Initialize(StorageType* t) {
+    VideoFrame_Private dummy;
+    *t = dummy.pp_video_frame();
+  }
 };
 
 }  // namespace internal