content: convert user action notification to observer usage

content/browser/user_metrics.cc

 // Copyright (c) 2011 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/public/browser/user_metrics.h"
 
 #include "base/bind.h"
+#include "base/lazy_instance.h"
+#include "base/observer_list.h"
 #include "content/public/browser/browser_thread.h"
-#include "content/public/browser/notification_service.h"
-#include "content/public/browser/notification_types.h"
 
 namespace content {
 namespace {
 
+base::LazyInstance<ObserverList<UserMetricsObserver> > g_observers =
+    LAZY_INSTANCE_INITIALIZER;
+
 // Forward declare because of circular dependency.
 void CallRecordOnUI(const std::string& action);
 
 void Record(const char *action) {
   if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
     BrowserThread::PostTask(
         BrowserThread::UI,
         FROM_HERE,
         base::Bind(&CallRecordOnUI, action));
     return;
   }
 
-  NotificationService::current()->Notify(
-      NOTIFICATION_USER_ACTION,
-      NotificationService::AllSources(),
-      Details<const char*>(&action));
+  FOR_EACH_OBSERVER(UserMetricsObserver, g_observers.Get(), UserAction(action));
 }
 
 void CallRecordOnUI(const std::string& action) {
   Record(action.c_str());
 }
 
 }  // namespace
 
 void RecordAction(const UserMetricsAction& action) {
   Record(action.str_);
 }
 
 void RecordComputedAction(const std::string& action) {
   Record(action.c_str());
 }
 
+void UserMetricsObserver::UserAction(const std::string& action) {
+}
+
+UserMetricsObserver::UserMetricsObserver() {
+  g_observers.Get().AddObserver(this);
+}
+
+UserMetricsObserver::~UserMetricsObserver() {
+  g_observers.Get().RemoveObserver(this);
+}
+
 }  // namespace content