Change PPB_VideoWriter Open function to return stream_id as out param.

ppapi/cpp/video_writer.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ppapi/cpp/video_writer.h"
 
 #include "ppapi/c/pp_errors.h"
 #include "ppapi/c/ppb_video_writer.h"
 #include "ppapi/cpp/instance_handle.h"
 #include "ppapi/cpp/module.h"
@@ skipping 24 matching lines @@
 }
 
 VideoWriter::VideoWriter(const VideoWriter& other)
     : Resource(other) {
 }
 
 VideoWriter::VideoWriter(PassRef, PP_Resource resource)
     : Resource(PASS_REF, resource) {
 }
 
-int32_t VideoWriter::Open(const std::string& stream_id,
-                          const CompletionCallback& cc) {
+int32_t VideoWriter::Open(const CompletionCallbackWithOutput<Var>& cc) {
   if (has_interface<PPB_VideoWriter_0_1>()) {
-    Var id(stream_id);
     int32_t result =
         get_interface<PPB_VideoWriter_0_1>()->Open(
             pp_resource(),
-            id.pp_var(), cc.pp_completion_callback());
+            cc.output(), cc.pp_completion_callback());
     return result;
   }
   return cc.MayForce(PP_ERROR_NOINTERFACE);
 }
 
 int32_t VideoWriter::PutFrame(const VideoFrame& frame) {
   if (has_interface<PPB_VideoWriter_0_1>()) {
     return get_interface<PPB_VideoWriter_0_1>()->PutFrame(
         pp_resource(),
         &frame.pp_video_frame());
   }
   return PP_ERROR_NOINTERFACE;
 }
 
 void VideoWriter::Close() {
   if (has_interface<PPB_VideoWriter_0_1>()) {
     get_interface<PPB_VideoWriter_0_1>()->Close(pp_resource());
   }
 }
 
 }  // namespace pp