Cleanup ash shelf accessor functions.

ash/root_window_controller.h

Index: ash/root_window_controller.h
diff --git a/ash/root_window_controller.h b/ash/root_window_controller.h
index 139b11e82ea02fbe452b7ed347d93b95e30b3a72..3e1f373d47326be7adea085c3b3210c0426d31e1 100644
--- a/ash/root_window_controller.h
+++ b/ash/root_window_controller.h
@@ -85,12 +85,6 @@ class ASH_EXPORT RootWindowController : public ShellObserver {
   // Creates and Initialize the RootWindowController for secondary displays.
   static void CreateForSecondaryDisplay(AshWindowTreeHost* host);
 
-  // Returns a RootWindowController that has a shelf for given
-  // |window|. This returns the RootWindowController for the |window|'s
-  // root window when multiple shelf mode is enabled, or the primary
-  // RootWindowController otherwise.
-  static RootWindowController* ForShelf(const aura::Window* window);
-
   // Returns a RootWindowController of the window's root window.
   static RootWindowController* ForWindow(const aura::Window* window);