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

ash/system/overview/overview_button_tray.cc

Index: ash/system/overview/overview_button_tray.cc
diff --git a/ash/system/overview/overview_button_tray.cc b/ash/system/overview/overview_button_tray.cc
index 1d68e628c369f783a5a4cd89ba6b173803e9a050..8a77d6885ac8334c0847c3e90881555fb965ab86 100644
--- a/ash/system/overview/overview_button_tray.cc
+++ b/ash/system/overview/overview_button_tray.cc
@@ -84,11 +84,7 @@ void OverviewButtonTray::OnOverviewModeEnded() {
   SetDrawBackgroundAsActive(false);
 }
 
-bool OverviewButtonTray::ClickedOutsideBubble() {
-  // This class has no bubbles dismiss, but acknowledge that the message was
-  // handled.
-  return true;
-}
+void OverviewButtonTray::ClickedOutsideBubble() {}
 
 base::string16 OverviewButtonTray::GetAccessibleNameForTray() {
   return l10n_util::GetStringUTF16(IDS_ASH_OVERVIEW_BUTTON_ACCESSIBLE_NAME);