Add UIControlsAsh that works with multiple root windows

ash/wm/window_properties.h

Index: ash/wm/window_properties.h
diff --git a/ash/wm/window_properties.h b/ash/wm/window_properties.h
index 9f79a44c439289285e1aa83fe519e28a7efe2552..760bcd430586996faa5cfa466a92f113a0fc592a 100644
--- a/ash/wm/window_properties.h
+++ b/ash/wm/window_properties.h
@@ -11,6 +11,10 @@
 #include "ui/aura/window.h"
 #include "ui/base/ui_base_types.h"
 
+namespace ui_controls {
+class UIControlsAura;
+}
+
 namespace ash {
 namespace internal {
 
@@ -31,6 +35,10 @@ extern const aura::WindowProperty<ui::WindowShowState>* const
 // window.  If unset, no shadow is displayed.
 extern const aura::WindowProperty<ShadowType>* const kShadowTypeKey;
 
+// Used to store a ui_controls for each root window.
+extern const aura::WindowProperty<ui_controls::UIControlsAura*>* const
+    kUIControlsKey;
+
 extern const aura::WindowProperty<WindowPersistsAcrossAllWorkspacesType>* const
     kWindowPersistsAcrossAllWorkspacesKey;