Add login time metric for chromeos.

chrome/browser/chromeos/browser_notification_observers.h

Index: chrome/browser/chromeos/browser_notification_observers.h
diff --git a/chrome/browser/chromeos/browser_notification_observers.h b/chrome/browser/chromeos/browser_notification_observers.h
index e2921af37effa42d4461ab98b9059b039dbc9ec4..13dacce76199090789bc226571ed55b4ef363d64 100644
--- a/chrome/browser/chromeos/browser_notification_observers.h
+++ b/chrome/browser/chromeos/browser_notification_observers.h
@@ -7,6 +7,7 @@
 
 #include "base/atomic_sequence_num.h"
 #include "base/singleton.h"
+#include "base/time.h"
 #include "chrome/common/notification_observer.h"
 #include "chrome/common/notification_registrar.h"
 #include "chrome/common/notification_source.h"
@@ -26,6 +27,10 @@ class InitialTabNotificationObserver : public NotificationObserver {
     return Singleton<InitialTabNotificationObserver>::get();
   }
 
+  void SetLoginSuccessTime() {
+    login_success_time_ = base::Time::NowFromSystemTime();
+  }
+
   // NotificationObserver implementation.
   virtual void Observe(NotificationType type,
                        const NotificationSource& source,
@@ -34,6 +39,7 @@ class InitialTabNotificationObserver : public NotificationObserver {
  private:
   NotificationRegistrar registrar_;
   base::AtomicSequenceNumber num_tabs_;
+  base::Time login_success_time_;
 
   DISALLOW_COPY_AND_ASSIGN(InitialTabNotificationObserver);
 };