Use SyncMessageFilter to Send() ipc messages from background threads.

content/renderer/render_thread_impl.cc

 // Copyright (c) 2012 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/renderer/render_thread_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <map>
 #include <vector>
@@ skipping 469 matching lines @@
   }
 
   if (CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kDomAutomationController)) {
     base::StringPiece extension = content::GetContentClient()->GetDataResource(
         IDR_DOM_AUTOMATION_JS);
     RegisterExtension(new v8::Extension(
         "dom_automation.js", extension.data(), 0, NULL, extension.size()));
   }
 
-  web_database_observer_impl_.reset(new WebDatabaseObserverImpl(Get()));
+  web_database_observer_impl_.reset(
+      new WebDatabaseObserverImpl(sync_message_filter()));
   WebKit::WebDatabase::setObserver(web_database_observer_impl_.get());
 
   WebRuntimeFeatures::enableSockets(
       !command_line.HasSwitch(switches::kDisableWebSockets));
 
   WebRuntimeFeatures::enableDatabase(
       !command_line.HasSwitch(switches::kDisableDatabases));
 
   WebRuntimeFeatures::enableDataTransferItems(
       !command_line.HasSwitch(switches::kDisableDataTransferItems));
@@ skipping 440 matching lines @@
 
 scoped_refptr<base::MessageLoopProxy>
 RenderThreadImpl::GetFileThreadMessageLoopProxy() {
   DCHECK(message_loop() == MessageLoop::current());
   if (!file_thread_.get()) {
     file_thread_.reset(new base::Thread("Renderer::FILE"));
     file_thread_->Start();
   }
   return file_thread_->message_loop_proxy();
 }