[Downloads/Phone] Add button to icon row for offlining pages

chrome/android/java/res/menu/main_menu.xml

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright 2015 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. -->
 
 <menu xmlns:android="http://schemas.android.com/apk/res/android">
     <!-- These menu items are common to tablet and phone. -->
     <group android:id="@+id/PAGE_MENU"
         android:visible="false">
         <item android:id="@+id/icon_row_menu_id"
             android:title="@null">
             <menu>
               <item android:id="@+id/forward_menu_id"
                 android:title="@string/accessibility_menu_forward"
                 android:icon="@drawable/btn_forward"/>
               <item android:id="@+id/bookmark_this_page_id"
                 android:title="@string/accessibility_menu_bookmark"
                 android:icon="@drawable/btn_star"/>
+              <item android:id="@+id/offline_page_id"
+                android:title="@string/contextmenu_save_offline"
+                android:icon="@drawable/ic_get_app_white_24dp"/>
               <item android:id="@+id/info_menu_id"
                 android:title="@string/accessibility_menu_info"
                 android:icon="@drawable/btn_info" />
               <item android:id="@+id/reload_menu_id"
                 android:title="@string/accessibility_btn_refresh"
                 android:icon="@drawable/btn_reload_stop"/>
             </menu>
         </item>
         <item android:id="@+id/update_menu_id"
             android:title="@string/menu_update"
@@ skipping 58 matching lines @@
         android:visible="false">
         <item android:id="@id/new_tab_menu_id"
             android:title="@string/menu_new_tab" />
         <item android:id="@id/new_incognito_tab_menu_id"
             android:title="@string/menu_new_incognito_tab" />
         <item android:id="@id/preferences_id"
             android:title="@string/menu_preferences" />
     </group>
 </menu>