WIP: Eliminate event.target() usage from TrayEventFilter

ash/pointer_watcher_delegate_aura.h

Index: ash/pointer_watcher_delegate_aura.h
diff --git a/ash/pointer_watcher_delegate_aura.h b/ash/pointer_watcher_delegate_aura.h
index 8a7eb662ca4232c8b88641da30528d4f3ee277fa..6832bcbf46bd75c4d19bb49f222d2bf39464ef7e 100644
--- a/ash/pointer_watcher_delegate_aura.h
+++ b/ash/pointer_watcher_delegate_aura.h
@@ -16,6 +16,10 @@ namespace ui {
 class LocatedEvent;
 }
 
+namespace views {
+class Widget;
+}
+
 namespace ash {
 
 // Support for PointerWatchers in non-mus ash, implemented with a pre-target
@@ -35,6 +39,7 @@ class ASH_EXPORT PointerWatcherDelegateAura : public PointerWatcherDelegate,
   void OnTouchEvent(ui::TouchEvent* event) override;
 
  private:
+  views::Widget* GetTargetWidget(const ui::LocatedEvent& event) const;
   gfx::Point GetLocationInScreen(const ui::LocatedEvent& event) const;
 
   // Must be empty on destruction.