workers: Introduce a WorkerMessageFilter to ease routing/processing worker messages.

content/child/navigator_connect/navigator_connect_dispatcher.cc

 // Copyright 2014 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/navigator_connect/navigator_connect_dispatcher.h"
 
-#include "base/message_loop/message_loop_proxy.h"
 #include "content/child/navigator_connect/navigator_connect_provider.h"
-#include "content/child/thread_safe_sender.h"
-#include "content/child/worker_thread_task_runner.h"
 #include "content/common/navigator_connect_messages.h"
 
 namespace content {
 
 NavigatorConnectDispatcher::NavigatorConnectDispatcher(ThreadSafeSender* sender)
-    : main_thread_loop_proxy_(base::MessageLoopProxy::current()),
-      thread_safe_sender_(sender) {
+    : WorkerThreadMessageFilter(sender) {
 }
 
 NavigatorConnectDispatcher::~NavigatorConnectDispatcher() {
 }
 
-base::TaskRunner* NavigatorConnectDispatcher::OverrideTaskRunnerForMessage(
-    const IPC::Message& msg) {
-  if (IPC_MESSAGE_CLASS(msg) != NavigatorConnectMsgStart)
-    return NULL;
-  int ipc_thread_id = 0;
-  const bool success = PickleIterator(msg).ReadInt(&ipc_thread_id);
-  DCHECK(success);
-  if (!ipc_thread_id)
-    return main_thread_loop_proxy_.get();
-  return new WorkerThreadTaskRunner(ipc_thread_id);
+bool NavigatorConnectDispatcher::ShouldHandleMessage(
+    const IPC::Message& msg) const {
+  return IPC_MESSAGE_CLASS(msg) == NavigatorConnectMsgStart;
 }
 
-bool NavigatorConnectDispatcher::OnMessageReceived(const IPC::Message& msg) {
-  if (IPC_MESSAGE_CLASS(msg) != NavigatorConnectMsgStart)
-    return false;
-  NavigatorConnectProvider::ThreadSpecificInstance(thread_safe_sender_.get(),
-                                                   main_thread_loop_proxy_)
-      ->OnMessageReceived(msg);
-  return true;
+void NavigatorConnectDispatcher::OnFilteredMessageReceived(
+    const IPC::Message& msg) {
+  NavigatorConnectProvider::ThreadSpecificInstance(
+      thread_safe_sender(), main_thread_task_runner())->OnMessageReceived(msg);
+}
+
+bool NavigatorConnectDispatcher::GetWorkerThreadIdForMessage(
+    const IPC::Message& msg,
+    int* ipc_thread_id) {
+  return PickleIterator(msg).ReadInt(ipc_thread_id);
 }
 
 }  // namespace content