Allow MessageFilters to restrict listening to specific message classes

extensions/browser/extension_message_filter.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 "extensions/browser/extension_message_filter.h"
 
 #include "chrome/common/extensions/extension_messages.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/resource_dispatcher_host.h"
 #include "extensions/browser/event_router.h"
 #include "extensions/browser/extension_system.h"
 #include "extensions/browser/process_manager.h"
 #include "ipc/ipc_message_macros.h"
 
 using content::BrowserThread;
 using content::RenderProcessHost;
 
 namespace extensions {
 
 ExtensionMessageFilter::ExtensionMessageFilter(int render_process_id,
                                                content::BrowserContext* context)
-    : render_process_id_(render_process_id), browser_context_(context) {
+    : BrowserMessageFilter(ExtensionMsgStart),
+      render_process_id_(render_process_id),
+      browser_context_(context) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 }
 
 ExtensionMessageFilter::~ExtensionMessageFilter() {}
 
 void ExtensionMessageFilter::OverrideThreadForMessage(
     const IPC::Message& message,
     BrowserThread::ID* thread) {
   switch (message.type()) {
     case ExtensionHostMsg_AddListener::ID:
@@ skipping 130 matching lines @@
   static int next_unique_id = 0;
   *unique_id = ++next_unique_id;
 }
 
 void ExtensionMessageFilter::OnExtensionResumeRequests(int route_id) {
   content::ResourceDispatcherHost::Get()->ResumeBlockedRequestsForRoute(
       render_process_id_, route_id);
 }
 
 }  // namespace extensions