[Extensions Page MD] Stub out a materialized extensions page

chrome/browser/ui/webui/chrome_web_ui_controller_factory.cc

 // Copyright (c) 2012 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/ui/webui/chrome_web_ui_controller_factory.h"
 
 #include <vector>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 380 matching lines @@
     return &NewWebUI<HelpUI>;
   // Identity API is not available on Android.
   if (url.host() == chrome::kChromeUIIdentityInternalsHost)
     return &NewWebUI<IdentityInternalsUI>;
   if (url.host() == chrome::kChromeUINewTabHost)
     return &NewWebUI<NewTabUI>;
   if (url.host() == chrome::kChromeUIMdSettingsHost &&
       ::switches::MdSettingsEnabled()) {
     return &NewWebUI<settings::MdSettingsUI>;
   }
+  // If the material design extensions page is enabled, it gets its own host.
+  // Otherwise, it's handled by the uber settings page.
+  if (url.host() == chrome::kChromeUIExtensionsHost &&
+      ::switches::MdExtensionsEnabled()) {
+    return &NewWebUI<extensions::ExtensionsUI>;
+  }
   if (url.host() == chrome::kChromeUIQuotaInternalsHost)
     return &NewWebUI<QuotaInternalsUI>;
   // Settings are implemented with native UI elements on Android.
   // Handle chrome://settings if settings in a window and about in settings
   // are enabled.
   if (url.host() == chrome::kChromeUISettingsFrameHost ||
       (url.host() == chrome::kChromeUISettingsHost &&
        ::switches::AboutInSettingsEnabled())) {
     return &NewWebUI<options::OptionsUI>;
   }
@@ skipping 353 matching lines @@
 #endif
 
   // Android doesn't use the plugins pages.
   if (page_url.host() == chrome::kChromeUIPluginsHost)
     return PluginsUI::GetFaviconResourceBytes(scale_factor);
 
 #endif
 
   return NULL;
 }