PPAPI: Initialize CompletionCallbackWithOutput storage

ppapi/cpp/private/pass_file_handle.h

Index: ppapi/cpp/private/pass_file_handle.h
diff --git a/ppapi/cpp/private/pass_file_handle.h b/ppapi/cpp/private/pass_file_handle.h
index 53f32dd58570a9dd04f23e3272fe4e3493cc2ec7..c25353b48389593fa880365dc13a012271f0d3b7 100644
--- a/ppapi/cpp/private/pass_file_handle.h
+++ b/ppapi/cpp/private/pass_file_handle.h
@@ -5,6 +5,8 @@
 #ifndef PPAPI_CPP_PRIVATE_PASS_FILE_HANDLE_H_
 #define PPAPI_CPP_PRIVATE_PASS_FILE_HANDLE_H_
 
+#include <string.h>
+
 #include "ppapi/c/private/pp_file_handle.h"
 #include "ppapi/cpp/output_traits.h"
 
@@ -67,6 +69,10 @@ struct CallbackOutputTraits<PassFileHandle> {
   static inline PassFileHandle StorageToPluginArg(StorageType& t) {
     return PassFileHandle(t);
   }
+
+  static inline void Initialize(StorageType* t) {
+    memset(t, 0, sizeof(*t));
+  }
 };
 
 }  // namespace internal