[MD Settings] Add feature to enable md-settings by default.

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 <stddef.h>
 
 #include <vector>
 
@@ skipping 392 matching lines @@
   // Otherwise, it's handled by the uber settings page.
   if (url.host() == chrome::kChromeUIExtensionsHost &&
       ::switches::MdExtensionsEnabled()) {
     return &NewWebUI<extensions::ExtensionsUI>;
   }
   // Material Design history is on its own host, rather than on an Uber page.
   if (base::FeatureList::IsEnabled(features::kMaterialDesignHistoryFeature) &&
       url.host() == chrome::kChromeUIHistoryHost) {
     return &NewWebUI<MdHistoryUI>;
   }
+  // Material Design Settings gets its own host, if enabled.
+  if (base::FeatureList::IsEnabled(features::kMaterialDesignSettingsFeature) &&
+      url.host() == chrome::kChromeUISettingsHost) {
+    return &NewWebUI<settings::MdSettingsUI>;
+  }
   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 75 matching lines @@
 
   // chrome://inspect isn't supported on Android nor iOS. Page debugging is
   // handled by a remote devtools on the host machine, and other elements, i.e.
   // extensions aren't supported.
   if (url.host() == chrome::kChromeUIInspectHost)
     return &NewWebUI<InspectUI>;
 #endif
 #if !defined(OS_CHROMEOS) && !defined(OS_ANDROID)
   if (url.host() == chrome::kChromeUIChromeSigninHost)
     return &NewWebUI<InlineLoginUI>;
   if (url.host() == chrome::kChromeUIUserManagerHost)

[Dan Beam, 2016/06/07 00:25:08]

should this also be checking whether MD settings is enabled?

[groby-ooo-7-16, 2016/06/07 00:27:39]

No, because we'd never get that host in the first place - the other check
switches us to a different host. 

[Dan Beam, 2016/06/07 00:32:36]

yeah, maybe this is where the check should go instead of in the other place

why would we ever want the same Chrome session to show different versions of the
user manager?

[groby-ooo-7-16, 2016/06/08 00:22:41]

You'd have to ask the user manager team :)

I'd like to constrain this CL to making settings work, without changing the
logic for other features.

[Dan Beam, 2016/06/08 00:24:25]

+mahmadi
this CL might the MD user manager not work correctly

     return &NewWebUI<UserManagerUI>;
   if (url.host() == chrome::kChromeUIMdUserManagerHost)
     return &NewWebUI<MDUserManagerUI>;
   if (url.host() == chrome::kChromeUISyncConfirmationHost)
     return &NewWebUI<SyncConfirmationUI>;
   if (url.host() == chrome::kChromeUIProfileSigninConfirmationHost)
     return &NewWebUI<ProfileSigninConfirmationUI>;
 #endif
 
   /****************************************************************************
@@ skipping 269 matching lines @@
 #endif
 
   // Android doesn't use the plugins pages.
   if (page_url.host() == chrome::kChromeUIPluginsHost)
     return PluginsUI::GetFaviconResourceBytes(scale_factor);
 
 #endif
 
   return NULL;
 }