cros-md: Remove the non-MD immersive mode code paths

ash/common/material_design/material_design_controller.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_MATERIAL_DESIGN_MATERIAL_DESIGN_CONTROLLER_H_
 #define ASH_COMMON_MATERIAL_DESIGN_MATERIAL_DESIGN_CONTROLLER_H_
 
 #include "ash/ash_export.h"
 #include "base/macros.h"
 
 namespace ash {
 
 // TODO(estade): deprecated, remove: crbug.com/690957
 class ASH_EXPORT MaterialDesignController {
  public:
   // Returns true.
   static bool IsShelfMaterial();
 
   // Returns true.
-  static bool IsImmersiveModeMaterial();
-
-  // Returns true.
   static bool IsSystemTrayMenuMaterial();
 
   // Returns true.
   static bool UseMaterialDesignSystemIcons();
 
  private:
   // Declarations only. Do not allow construction of an object.
   MaterialDesignController();
   ~MaterialDesignController();
 
   DISALLOW_COPY_AND_ASSIGN(MaterialDesignController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_MATERIAL_DESIGN_MATERIAL_DESIGN_CONTROLLER_H_