mash: Close the system tray bubble on click outside its bounds

ash/system/web_notification/web_notification_tray.cc

Index: ash/system/web_notification/web_notification_tray.cc
diff --git a/ash/system/web_notification/web_notification_tray.cc b/ash/system/web_notification/web_notification_tray.cc
index 69694638968580654343609f12976f0f9358abd0..91ae20c33e44e7b764385cda9640fa20ac689d33 100644
--- a/ash/system/web_notification/web_notification_tray.cc
+++ b/ash/system/web_notification/web_notification_tray.cc
@@ -458,13 +458,12 @@ void WebNotificationTray::UpdateTrayContent() {
   SchedulePaint();
 }
 
-bool WebNotificationTray::ClickedOutsideBubble() {
+void WebNotificationTray::ClickedOutsideBubble() {
   // Only hide the message center
   if (!message_center_bubble())
-    return false;
+    return;
 
   message_center_tray_->HideMessageCenterBubble();
-  return true;
 }
 
 message_center::MessageCenter* WebNotificationTray::message_center() const {