Add extensions code to use common updater in components/update_client/

extensions/shell/common/switches.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 "extensions/shell/common/switches.h"
 
 namespace extensions {
 namespace switches {
 
 // Allow roaming in the cellular network.
 const char kAppShellAllowRoaming[] = "app-shell-allow-roaming";
 
 // Size for the host window to create (i.e. "800x600").
 const char kAppShellHostWindowSize[] = "app-shell-host-window-size";
 
-// ID of an extension CRX to be downloaded from the web store.
-const char kAppShellInstallCrx[] = "app-shell-install-crx";
-
 // SSID of the preferred WiFi network.
 const char kAppShellPreferredNetwork[] = "app-shell-preferred-network";
 
 // Refresh token for identity API calls for the current user. Used for testing.
 const char kAppShellRefreshToken[] = "app-shell-refresh-token";
 
 // User email address of the current user.
 const char kAppShellUser[] = "app-shell-user";
 
 }  // namespace switches
 }  // namespace extensions