Move event handler to window_selector to ensure correct lifetime.

ash/wm/overview/window_selector.h

Index: ash/wm/overview/window_selector.h
diff --git a/ash/wm/overview/window_selector.h b/ash/wm/overview/window_selector.h
index 7536f41ae8aa76620d22a47fb809fea1090e2ea5..4059540df807ca7de1fef563421c8d2a6f8e2167 100644
--- a/ash/wm/overview/window_selector.h
+++ b/ash/wm/overview/window_selector.h
@@ -20,7 +20,7 @@ class RootWindow;
 }
 
 namespace ui {
-class LocatedEvent;
+class EventHandler;
 }
 
 namespace ash {
@@ -101,6 +101,10 @@ class ASH_EXPORT WindowSelector
   // The window selection mode.
   Mode mode_;
 
+  // An event handler listening for the release of the alt key during alt-tab
+  // cycling.
+  scoped_ptr<ui::EventHandler> event_handler_;
+
   base::DelayTimer<WindowSelector> start_overview_timer_;
   scoped_ptr<WindowOverview> window_overview_;