content: convert user action notification to observer usage

chrome/browser/metrics/metrics_service.h

Index: chrome/browser/metrics/metrics_service.h
diff --git a/chrome/browser/metrics/metrics_service.h b/chrome/browser/metrics/metrics_service.h
index 308fe57ba1db9653251effc95e3bf085f6b34f16..ee5a849796a250bd3d8b09a424f025c3238a83df 100644
--- a/chrome/browser/metrics/metrics_service.h
+++ b/chrome/browser/metrics/metrics_service.h
@@ -24,6 +24,7 @@
 #include "chrome/installer/util/google_update_settings.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
+#include "content/public/browser/user_metrics.h"
 #include "net/url_request/url_fetcher_delegate.h"
 
 #if defined(OS_CHROMEOS)
@@ -137,6 +138,8 @@ class MetricsService
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  void OnUserAction(const std::string& action);
+
   // Invoked when we get a WM_SESSIONEND. This places a value in prefs that is
   // reset when RecordCompletedSessionEnd is invoked.
   void RecordStartOfSessionEnd();
@@ -398,9 +401,7 @@ class MetricsService
                        const content::NotificationDetails& details);
 
   // Checks whether a notification can be logged.
-  bool CanLogNotification(int type,
-                          const content::NotificationSource& source,
-                          const content::NotificationDetails& details);
+  bool CanLogNotification();
 
   // Sets the value of the specified path in prefs and schedules a save.
   void RecordBooleanPrefValue(const char* path, bool value);