Remove dead code related to Notification View Bubble

ash/common/system/web_notification/web_notification_tray.cc

Index: ash/common/system/web_notification/web_notification_tray.cc
diff --git a/ash/common/system/web_notification/web_notification_tray.cc b/ash/common/system/web_notification/web_notification_tray.cc
index 0cbd26d5899eb95ff4b9eb327855071e71670a80..c6487da949363e3fb1ad3024c5f3515618ad3942 100644
--- a/ash/common/system/web_notification/web_notification_tray.cc
+++ b/ash/common/system/web_notification/web_notification_tray.cc
@@ -442,10 +442,6 @@ bool WebNotificationTray::IsMessageCenterBubbleVisible() const {
           message_center_bubble()->bubble()->IsVisible());
 }
 
-bool WebNotificationTray::IsMouseInNotificationBubble() const {
-  return false;
-}
-
 void WebNotificationTray::ShowMessageCenterBubble() {
   if (!IsMessageCenterBubbleVisible())
     message_center_tray_->ShowMessageCenterBubble();