content: convert user action notification to observer usage

content/browser/user_metrics.cc

Index: content/browser/user_metrics.cc
diff --git a/content/browser/user_metrics.cc b/content/browser/user_metrics.cc
index 927f3977d6b589f3363ca1c3d9b4a594d48c36ff..e352bfe8079f0bc17dba3aeb5fe7cbe823f6dfad 100644
--- a/content/browser/user_metrics.cc
+++ b/content/browser/user_metrics.cc
@@ -5,13 +5,16 @@
 #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);
 
@@ -24,10 +27,7 @@ void Record(const char *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) {
@@ -44,4 +44,15 @@ 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