Register a separate default ui::EventTarget for Aura (Ash) to ensure that it does not interfere wit…

ui/aura/root_window.h

Index: ui/aura/root_window.h
===================================================================
--- ui/aura/root_window.h	(revision 163961)
+++ ui/aura/root_window.h	(working copy)
@@ -283,6 +283,10 @@
   // Exposes RootWindowHost::QueryMouseLocation() for test purposes.
   gfx::Point QueryMouseLocationForTest() const;
 
+  void set_parent_event_target(ui::EventTarget* parent_event_target) {
+    parent_event_target_ = parent_event_target;
+  }
+
  private:
   friend class Window;
   friend class CompositorLock;
@@ -413,6 +417,10 @@
   CompositorLock* compositor_lock_;
   bool draw_on_compositor_unlock_;
 
+  // Set to parent EventTarget if any. If this is set to NULL, we default to
+  // EventTarget implemented by the Aura Environment.
+  ui::EventTarget* parent_event_target_;
+
   DISALLOW_COPY_AND_ASSIGN(RootWindow);
 };