Lazy initialization for ProcessesEventRouter.

chrome/browser/extensions/api/processes/processes_api_service.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 "chrome/browser/extensions/api/processes/processes_api_service.h"
+
+#include "chrome/browser/extensions/event_router.h"
+#include "chrome/browser/extensions/extension_system.h"
+#include "chrome/browser/extensions/api/processes/processes_api.h"
+#include "chrome/browser/extensions/api/processes/processes_api_constants.h"
+#include "chrome/browser/extensions/api/processes/processes_api_service_factory.h"
+#include "chrome/browser/profiles/profile.h"
+
+namespace extensions {
+
+ProcessesAPIService::ProcessesAPIService(Profile* profile) : profile_(profile) {
+  DCHECK(ExtensionSystem::Get(profile_)->event_router());
+  ExtensionSystem::Get(profile_)->event_router()->RegisterObserver(
+      this, processes_api_constants::kOnUpdated);
+  ExtensionSystem::Get(profile_)->event_router()->RegisterObserver(
+      this, processes_api_constants::kOnUpdatedWithMemory);
+}
+
+ProcessesAPIService::~ProcessesAPIService() {
+}
+
+// static
+ProcessesAPIService* ProcessesAPIService::Get(Profile* profile) {
+  return ProcessesAPIServiceFactory::GetForProfile(profile);
+}
+
+void ProcessesAPIService::OnListenerAdded(const std::string& event_name) {
+  if (!processes_event_router_)
+    processes_event_router_.reset(new ProcessesEventRouter(profile_));
+  // We lazily tell the TaskManager to start updating when listeners to the
+  // processes.onUpdated or processes.onUpdatedWithMemory events arrive.
+  processes_event_router_->ListenerAdded();
+}
+
+void ProcessesAPIService::OnListenerRemoved(const std::string& event_name) {
+  // If a processes.onUpdated or processes.onUpdatedWithMemory event listener
+  // is removed (or a process with one exits), then we let the extension API
+  // know that it has one fewer listener.
+  processes_event_router_->ListenerRemoved();
+}
+
+}  // namespace extensions