Stop notification updates from unpausing toast timers.

ui/message_center/popup_timer.h

Index: ui/message_center/popup_timer.h
diff --git a/ui/message_center/popup_timer.h b/ui/message_center/popup_timer.h
index 494e360b88b1e34ee11cf0bc87e1d99f8554722b..8137d3d2fe93677ccbfe5b5e2e232d19f1bf56c1 100644
--- a/ui/message_center/popup_timer.h
+++ b/ui/message_center/popup_timer.h
@@ -41,6 +41,9 @@ class PopupTimer {
   // subsequent calls to Start the timer will continue where it left off.
   void Pause();
 
+  // Returns whether the underlying timer is running or not.
+  bool IsRunning() { return timer_->IsRunning(); }
+
  private:
   // Notification ID for which this timer applies.
   const std::string id_;