[Thread Safety] Replace WebString bound by cross-thread base::Bind() with base::string16

content/child/service_worker/web_service_worker_impl.cc

 // Copyright 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 "content/child/service_worker/web_service_worker_impl.h"
 
 #include "content/child/service_worker/service_worker_dispatcher.h"
 #include "content/child/service_worker/service_worker_handle_reference.h"
 #include "content/child/thread_safe_sender.h"
 #include "content/child/webmessageportchannel_impl.h"
 #include "content/common/service_worker/service_worker_messages.h"
 #include "third_party/WebKit/public/platform/WebServiceWorkerProxy.h"
 #include "third_party/WebKit/public/platform/WebString.h"
 
 using blink::WebMessagePortChannel;
 using blink::WebMessagePortChannelArray;
 using blink::WebMessagePortChannelClient;
 using blink::WebString;
 
 namespace content {
 
 namespace {
 
 void SendPostMessageToWorkerOnMainThread(
     ThreadSafeSender* thread_safe_sender,
     int handle_id,
-    const WebString& message,
+    const base::string16& message,
     scoped_ptr<WebMessagePortChannelArray> channels) {
   thread_safe_sender->Send(new ServiceWorkerHostMsg_PostMessageToWorker(
       handle_id, message,
       WebMessagePortChannelImpl::ExtractMessagePortIDs(channels.Pass())));
 }
 
 }  // namespace
 
 WebServiceWorkerImpl::WebServiceWorkerImpl(
     scoped_ptr<ServiceWorkerHandleReference> handle_ref,
@@ skipping 45 matching lines @@
       ServiceWorkerDispatcher::GetThreadSpecificInstance();
   DCHECK(dispatcher);
 
   // This may send channels for MessagePorts, and all internal book-keeping
   // messages for MessagePort (e.g. QueueMessages) are sent from main thread
   // (with thread hopping), so we need to do the same thread hopping here not
   // to overtake those messages.
   dispatcher->main_thread_task_runner()->PostTask(
       FROM_HERE, base::Bind(&SendPostMessageToWorkerOnMainThread,
                             thread_safe_sender_, handle_ref_->handle_id(),
-                            message, base::Passed(make_scoped_ptr(channels))));
+                            // We cast WebString to string16 before crossing
+                            // threads for thread-safety.
+                            static_cast<base::string16>(message),
+                            base::Passed(make_scoped_ptr(channels))));
 }
 
 void WebServiceWorkerImpl::terminate() {
   thread_safe_sender_->Send(
       new ServiceWorkerHostMsg_TerminateWorker(handle_ref_->handle_id()));
 }
 
 }  // namespace content