Make ui_controls only usable from interactive_ui_tests. This has two benefits:

ash/wm/window_properties.h

Index: ash/wm/window_properties.h
===================================================================
--- ash/wm/window_properties.h	(revision 176470)
+++ ash/wm/window_properties.h	(working copy)
@@ -14,10 +14,6 @@
 class Rect;
 }
 
-namespace ui_controls {
-class UIControlsAura;
-}
-
 namespace ash {
 class FramePainter;
 namespace internal {
@@ -64,10 +60,6 @@
 ASH_EXPORT extern const aura::WindowProperty<bool>* const
     kStayInSameRootWindowKey;
 
-// Used to store a ui_controls for each root window.
-extern const aura::WindowProperty<ui_controls::UIControlsAura*>* const
-    kUIControlsKey;
-
 // A property key to remember if a windows position or size was changed by a
 // user.
 ASH_EXPORT extern const aura::WindowProperty<bool>* const