Adds views::corewm::WMState to install common state

ui/aura/client/window_stacking_client.h

Index: ui/aura/client/window_stacking_client.h
diff --git a/ui/aura/client/window_stacking_client.h b/ui/aura/client/window_stacking_client.h
index b4576c59426ddecb540fa9e439b7f999be026687..848260397cb59ef6e1933709a4b7a7026fb9e7db 100644
--- a/ui/aura/client/window_stacking_client.h
+++ b/ui/aura/client/window_stacking_client.h
@@ -15,16 +15,21 @@ namespace client {
 
 class AURA_EXPORT WindowStackingClient {
  public:
-  virtual ~WindowStackingClient() {}
-
   // Invoked from the various Window stacking functions. Allows the
   // WindowStackingClient to alter the source, target and/or direction to stack.
-  virtual void AdjustStacking(Window** child,
+  // Returns true if stacking should continue; false if the stacking should not
+  // happen.
+  virtual bool AdjustStacking(Window** child,
                               Window** target,
                               Window::StackDirection* direction) = 0;
+
+ protected:
+  virtual ~WindowStackingClient() {}
 };
 
-// Sets/gets the WindowStackingClient. The setter takes ownership of |client|.
+// Sets/gets the WindowStackingClient. This does *not* take ownership of
+// |client|. It is assumed the caller will invoke SetWindowStackingClient(NULL)
+// before deleting |client|.
 AURA_EXPORT void SetWindowStackingClient(WindowStackingClient* client);
 AURA_EXPORT WindowStackingClient* GetWindowStackingClient();