AcceleratorProvider: Make GetAcceleratorForCommandId const.

chrome/browser/renderer_context_menu/mock_render_view_context_menu.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 CHROME_BROWSER_RENDERER_CONTEXT_MENU_MOCK_RENDER_VIEW_CONTEXT_MENU_H_
 #define CHROME_BROWSER_RENDERER_CONTEXT_MENU_MOCK_RENDER_VIEW_CONTEXT_MENU_H_
 
 #include <cstddef>
 #include <memory>
 #include <vector>
@@ skipping 34 matching lines @@
   explicit MockRenderViewContextMenu(bool incognito);
   ~MockRenderViewContextMenu() override;
 
   // SimpleMenuModel::Delegate implementation.
   bool IsCommandIdChecked(int command_id) const override;
   bool IsCommandIdEnabled(int command_id) const override;
   void ExecuteCommand(int command_id, int event_flags) override;
   void MenuWillShow(ui::SimpleMenuModel* source) override;
   void MenuClosed(ui::SimpleMenuModel* source) override;
   bool GetAcceleratorForCommandId(int command_id,
-                                  ui::Accelerator* accelerator) override;
+                                  ui::Accelerator* accelerator) const override;
 
   // RenderViewContextMenuProxy implementation.
   void AddMenuItem(int command_id, const base::string16& title) override;
   void AddCheckItem(int command_id, const base::string16& title) override;
   void AddSeparator() override;
   void AddSubMenu(int command_id,
                   const base::string16& label,
                   ui::MenuModel* model) override;
   void UpdateMenuItem(int command_id,
                       bool enabled,
@@ skipping 30 matching lines @@
   // Either |original_profile_| or its incognito profile.
   Profile* profile_;
 
   // A list of menu items added.
   std::vector<MockMenuItem> items_;
 
   DISALLOW_COPY_AND_ASSIGN(MockRenderViewContextMenu);
 };
 
 #endif  // CHROME_BROWSER_RENDERER_CONTEXT_MENU_MOCK_RENDER_VIEW_CONTEXT_MENU_H_