Use explicit WebString <-> string conversion methods for workers

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 <utility>
 
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
@@ skipping 99 matching lines @@
 
   // 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,
                  base::RetainedRef(thread_safe_sender_),
                  handle_ref_->handle_id(), provider_impl->provider_id(),
-                 // We cast WebString to string16 before crossing
+                 // We convert WebString to string16 before crossing
                  // threads for thread-safety.
-                 static_cast<base::string16>(message),
-                 url::Origin(source_origin),
+                 message.utf16(), url::Origin(source_origin),

[falken, 2016/12/26 01:26:20]

Do you know why this IPC should be a string16 and not just std::string?

                  base::Passed(base::WrapUnique(channels))));
 }
 
 void WebServiceWorkerImpl::terminate() {
   thread_safe_sender_->Send(
       new ServiceWorkerHostMsg_TerminateWorker(handle_ref_->handle_id()));
 }
 
 // static
 std::unique_ptr<blink::WebServiceWorker::Handle>
 WebServiceWorkerImpl::CreateHandle(
     const scoped_refptr<WebServiceWorkerImpl>& worker) {
   if (!worker)
     return nullptr;
   return base::MakeUnique<HandleImpl>(worker);
 }
 
 WebServiceWorkerImpl::~WebServiceWorkerImpl() {
   ServiceWorkerDispatcher* dispatcher =
       ServiceWorkerDispatcher::GetThreadSpecificInstance();
   if (dispatcher)
     dispatcher->RemoveServiceWorker(handle_ref_->handle_id());
 }
 
 }  // namespace content