Move the concept of Activation to the Shell.

ui/aura_shell/window_util.h

Index: ui/aura_shell/window_util.h
===================================================================
--- ui/aura_shell/window_util.h	(revision 114022)
+++ ui/aura_shell/window_util.h	(working copy)
@@ -17,6 +17,19 @@
 // Returns true if |window| is in the maximized state.
 AURA_SHELL_EXPORT bool IsWindowMaximized(aura::Window* window);
 
+// Convenience setters/getters for |aura::kRootWindowActiveWindow|.
+AURA_SHELL_EXPORT void ActivateWindow(aura::Window* window);
+AURA_SHELL_EXPORT void DeactivateWindow(aura::Window* window);
+AURA_SHELL_EXPORT bool IsActiveWindow(aura::Window* window);
+AURA_SHELL_EXPORT aura::Window* GetActiveWindow();
+
+// Retrieves the activatable window for |window|. If |window| is activatable,
+// this will just return it, otherwise it will climb the parent/transient parent
+// chain looking for a window that is activatable, per the ActivationController.
+// If you're looking for a function to get the activatable "top level" window,
+// this is probably what you're looking for.
+AURA_SHELL_EXPORT aura::Window* GetActivatableWindow(aura::Window* window);
+
 }  // namespace aura_shell
 
 #endif  // UI_AURA_SHELL_WINDOW_UTIL_H_