Second attempt at moving the StackingClient to a property on the RootWindow.

ui/aura/client/aura_constants.h

Index: ui/aura/client/aura_constants.h
===================================================================
--- ui/aura/client/aura_constants.h	(revision 114527)
+++ ui/aura/client/aura_constants.h	(working copy)
@@ -30,22 +30,26 @@
 // of the value is |gfx::Rect*|.
 AURA_EXPORT extern const char kRestoreBoundsKey[];
 
+// A property key to store a client that handles window activation. The type of
+// the value is |aura::ActivationClient*|.
+AURA_EXPORT extern const char kRootWindowActivationClient[];
+
+// A property key to store what the client defines as the active window on the
+// RootWindow. The type of the value is |aura::Window*|.
+AURA_EXPORT extern const char kRootWindowActiveWindow[];
+
 // A property key to store the drag and drop client for the root window. The
 // type of the value is |aura::DragDropClient*|.
 AURA_EXPORT extern const char kRootWindowDragDropClientKey[];
 
+// A property key to store a client that handles window parenting. The type of
+// the value is |aura::client::StackingClient*|.
+AURA_EXPORT extern const char kRootWindowStackingClient[];
+
 // A property key to store the tooltip client for the root window. The type of
 // the value is |aura::TooltipClient*|.
 AURA_EXPORT extern const char kRootWindowTooltipClientKey[];
 
-// A property key to store what the client defines as the active window on the
-// RootWindow. The type of the value is |aura::Window*|.
-AURA_EXPORT extern const char kRootWindowActiveWindow[];
-
-// A property key to store a client that handles window activation. The type of
-// the value is |aura::ActivationClient*|.
-AURA_EXPORT extern const char kRootWindowActivationClient[];
-
 // A property key for a value from aura::ShadowType describing the drop shadow
 // that should be displayed under the window.  If unset, no shadow is displayed.
 AURA_EXPORT extern const char kShadowTypeKey[];