Avoid copying the data string when posting ImportantFileWriter write tasks

components/bookmarks/browser/bookmark_storage.cc

 // Copyright 2014 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 "components/bookmarks/browser/bookmark_storage.h"
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
 #include "base/files/file_util.h"
 #include "base/json/json_file_value_serializer.h"
@@ skipping 187 matching lines @@
 }
 
 bool BookmarkStorage::SaveNow() {
   if (!model_ || !model_->loaded()) {
     // We should only get here if we have a valid model and it's finished
     // loading.
     NOTREACHED();
     return false;
   }
 
-  std::string data;
-  if (!SerializeData(&data))
+  scoped_ptr<std::string> data(new std::string);
+  if (!SerializeData(data.get()))
     return false;
-  writer_.WriteNow(data);
+  writer_.WriteNow(data.Pass());
   return true;
 }
 
 }  // namespace bookmarks