mash shelf: Don't create shelf DimmerView in ShelfWidget on mus

ash/common/shelf/wm_shelf.h

 // Copyright 2016 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_COMMON_SHELF_WM_SHELF_H_
 #define ASH_COMMON_SHELF_WM_SHELF_H_
 
 #include "ash/ash_export.h"
 #include "ash/common/shelf/shelf_types.h"
 
 namespace gfx {
 class Rect;
 }
 
 namespace ui {
 class GestureEvent;
 }
 
 namespace ash {
 
 class ShelfLockingManager;
 class ShelfView;
+class WmDimmerView;
 class WmShelfObserver;
 class WmWindow;
 
 // Used for accessing global state.
 class ASH_EXPORT WmShelf {
  public:
   // Returns the window showing the shelf.
   virtual WmWindow* GetWindow() = 0;
 
   virtual ShelfAlignment GetAlignment() const = 0;
@@ skipping 12 matching lines @@
   virtual void SetAutoHideBehavior(ShelfAutoHideBehavior behavior) = 0;
 
   virtual ShelfAutoHideState GetAutoHideState() const = 0;
 
   // Invoke when the auto-hide state may have changed (for example, when the
   // system tray bubble opens it should force the shelf to be visible).
   virtual void UpdateAutoHideState() = 0;
 
   virtual ShelfBackgroundType GetBackgroundType() const = 0;
 
+  // Creates a view that dims shelf items. The returned view is owned by its
+  // widget. Returns null if shelf dimming is not supported (e.g. on mus).
+  // TODO(jamescook): Delete this after material design ships, as MD will not
+  // require shelf dimming. http://crbug.com/614453
+  virtual WmDimmerView* CreateDimmerView(bool disable_animations_for_test) = 0;
+
   // Shelf items are slightly dimmed (e.g. when a window is maximized).
+  // TODO(jamescook): Delete this after material design ships, as MD will not
+  // require shelf dimming. http://crbug.com/614453
   virtual bool IsDimmed() const = 0;
 
   // Whether the shelf item overflow bubble is visible.
   // TODO(jamescook): Eliminate when ShelfView moves to //ash/common.
   // http://crbug.com/615155
   virtual bool IsShowingOverflowBubble() const = 0;
 
   // Schedules a repaint for all shelf buttons.
   // TODO(jamescook): Eliminate when ShelfView moves to //ash/common.
   // http://crbug.com/615155
@@ skipping 33 matching lines @@
   virtual ShelfLockingManager* GetShelfLockingManagerForTesting() = 0;
   virtual ShelfView* GetShelfViewForTesting() = 0;
 
  protected:
   virtual ~WmShelf() {}
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SHELF_WM_SHELF_H_