Pass shelf instances, not root windows, for ash context menus.

ash/shell.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_SHELL_H_
 #define ASH_SHELL_H_
 
 #include <utility>
 #include <vector>
 
@@ skipping 445 matching lines @@
   // TODO(oshima): Define an interface to access shelf/launcher
   // state, or just use Launcher.
 
   // Sets/gets the shelf auto-hide behavior on |root_window|.
   void SetShelfAutoHideBehavior(ShelfAutoHideBehavior behavior,
                                 aura::Window* root_window);
   ShelfAutoHideBehavior GetShelfAutoHideBehavior(
       aura::Window* root_window) const;
 
   // Sets/gets shelf's alignment on |root_window|.
-  void SetShelfAlignment(ShelfAlignment alignment,
-                         aura::Window* root_window);
-  ShelfAlignment GetShelfAlignment(const aura::Window* root_window);
+  void SetShelfAlignment(ShelfAlignment alignment, aura::Window* root_window);
+  ShelfAlignment GetShelfAlignment(const aura::Window* root_window) const;
+
+  // Called when the alignment for a shelf changes.
+  void OnShelfAlignmentChanged(aura::Window* root_window);
 
   // Notifies |observers_| when entering or exiting fullscreen mode in
   // |root_window|.
   void NotifyFullscreenStateChange(bool is_fullscreen,
                                    aura::Window* root_window);
 
   // Creates a modal background (a partially-opaque fullscreen window)
   // on all displays for |window|.
   void CreateModalBackground(aura::Window* window);
 
@@ skipping 291 matching lines @@
   bool in_mus_ = false;
 
   scoped_ptr<KeyboardUI> keyboard_ui_;
 
   DISALLOW_COPY_AND_ASSIGN(Shell);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELL_H_