Add simple mash context menu support.

chrome/browser/ui/ash/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_UI_ASH_CONTEXT_MENU_H_
+#define CHROME_BROWSER_UI_ASH_CONTEXT_MENU_H_
+
+#include "mash/shelf/public/interfaces/context_menu.mojom.h"
+
+// Chrome's delegate for mash context menus.
+class ContextMenu : public mash::shelf::mojom::ContextMenu {
+ public:
+  ContextMenu();
+  ~ContextMenu() override;
+
+  // mash::shelf::mojom::ContextMenu:
+  void GetItemsAndInfo(uint32_t shelf_item_type,
+                       int32_t shelf_item_id,
+                       const GetItemsAndInfoCallback& callback) override;
+  void ExecuteCommand(int32_t command_id, int32_t event_flags) override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ContextMenu);
+};
+
+#endif  // CHROME_BROWSER_UI_ASH_CONTEXT_MENU_H_