[Merge to M51] ServiceWorker: Remove a bad IPC message check on postMessage()

content/browser/service_worker/service_worker_dispatcher_host.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/browser/service_worker/service_worker_dispatcher_host.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "base/macros.h"
@@ skipping 678 matching lines @@
 
   ServiceWorkerHandle* handle = handles_.Lookup(handle_id);
   if (!handle) {
     bad_message::ReceivedBadMessage(this, bad_message::SWDH_POST_MESSAGE);
     return;
   }
 
   ServiceWorkerProviderHost* sender_provider_host =
       GetContext()->GetProviderHost(render_process_id_, provider_id);
   if (!sender_provider_host) {
-    bad_message::ReceivedBadMessage(this, bad_message::SWDH_POST_MESSAGE);
+    // This may occur when destruction of the sender provider overtakes
+    // postMessage() because of thread hopping on WebServiceWorkerImpl.
     return;
   }
 
   DispatchExtendableMessageEvent(
       make_scoped_refptr(handle->version()), message, source_origin,
       sent_message_ports, sender_provider_host,
       base::Bind(&ServiceWorkerUtils::NoOpStatusCallback));
 }
 
 void ServiceWorkerDispatcherHost::DispatchExtendableMessageEvent(
@@ skipping 716 matching lines @@
   if (!handle) {
     bad_message::ReceivedBadMessage(this,
                                     bad_message::SWDH_TERMINATE_BAD_HANDLE);
     return;
   }
   handle->version()->StopWorker(
       base::Bind(&ServiceWorkerUtils::NoOpStatusCallback));
 }
 
 }  // namespace content