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

content/worker/worker_thread.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/worker/worker_thread.h"
 
 #include "base/command_line.h"
 #include "base/lazy_instance.h"
 #include "base/threading/thread_local.h"
 #include "content/common/appcache/appcache_dispatcher.h"
@@ skipping 17 matching lines @@
     LAZY_INSTANCE_INITIALIZER;
 
 
 WorkerThread::WorkerThread() {
   lazy_tls.Pointer()->Set(this);
   webkit_platform_support_.reset(new WorkerWebKitPlatformSupportImpl);
   WebKit::initialize(webkit_platform_support_.get());
 
   appcache_dispatcher_.reset(new AppCacheDispatcher(this));
 
-  web_database_observer_impl_.reset(new WebDatabaseObserverImpl(this));
+  web_database_observer_impl_.reset(
+      new WebDatabaseObserverImpl(sync_message_filter()));
   WebKit::WebDatabase::setObserver(web_database_observer_impl_.get());
   db_message_filter_ = new DBMessageFilter();
   channel()->AddFilter(db_message_filter_.get());
 
   indexed_db_message_filter_ = new IndexedDBMessageFilter;
   channel()->AddFilter(indexed_db_message_filter_.get());
 
   const CommandLine& command_line = *CommandLine::ForCurrentProcess();
 
   webkit_glue::EnableWebCoreLogChannels(
@@ skipping 69 matching lines @@
   }
 }
 
 void WorkerThread::RemoveWorkerStub(WebSharedWorkerStub* stub) {
   worker_stubs_.erase(stub);
 }
 
 void WorkerThread::AddWorkerStub(WebSharedWorkerStub* stub) {
   worker_stubs_.insert(stub);
 }