aura: Move Window::ContainsMouse() implementation into the test API.

ui/aura/window.h

Index: ui/aura/window.h
diff --git a/ui/aura/window.h b/ui/aura/window.h
index dd086975eb1d4adc82a9127a238a46208cfe2320..52f941dee7910992306de311bfc571a8d4781d0e 100644
--- a/ui/aura/window.h
+++ b/ui/aura/window.h
@@ -471,9 +471,6 @@ class AURA_EXPORT Window : public ui::LayerDelegate,
   // Updates the layer name based on the window's name and id.
   void UpdateLayerName();
 
-  // Returns true if the mouse is currently within our bounds.
-  bool ContainsMouse();
-
   // Returns the first ancestor (starting at |this|) with a layer. |offset| is
   // set to the offset from |this| to the first ancestor with a layer. |offset|
   // may be NULL.