Separate out logic to handle different category/group of context menu items from RVContextMenu class

chrome/browser/tab_contents/menu_category_app_mode.cc

+// Copyright 2014 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.
+
+#include "chrome/browser/tab_contents/menu_category_app_mode.h"
+
+MenuCategoryAppMode::MenuCategoryAppMode(
+    content::RenderFrameHost* render_frame_host,
+    const content::ContextMenuParams& params)
+    : MenuCategoryBase(render_frame_host, params) {
+}
+
+MenuCategoryAppMode::~MenuCategoryAppMode() {
+}
+
+bool MenuCategoryAppMode::IsCategoryEnabled(int category) {
+  switch (category) {
+    case ITEM_CATEGORY_EDITABLE:
+    case ITEM_CATEGORY_COPY:
+      return MenuCategoryBase::IsCategoryEnabled(category);
+    default:
+      return false;
+  }
+}