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

chrome/browser/ui/chrome_pages.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_CHROME_PAGES_H_
 #define CHROME_BROWSER_UI_CHROME_PAGES_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 39 matching lines @@
 // |browser| should be NULL if there are no currently open browser windows.
 void ShowFeedbackPage(Browser* browser,
                       const std::string& description_template,
                       const std::string& category_tag);
 
 void ShowHelp(Browser* browser, HelpSource source);
 void ShowHelpForProfile(Profile* profile, HelpSource source);
 void ShowPolicy(Browser* browser);
 void ShowSlow(Browser* browser);
 
+// For the transition to Material Design settings, Chrome needs to temporarily
+// support two different settings pages - "legacy" and "MD Settings". Depending
+// on a feature flag, chrome://settings will point to one of them, while the
+// other one is reachable via chrome://legacy-settings and chrome://md-settings,
+// respectively.
+std::string GetLegacySettingsHost();
+std::string GetMdSettingsHost();
+
 // Constructs a settings GURL for the specified |sub_page|.
 GURL GetSettingsUrl(const std::string& sub_page);
 
 // Returns true if |url| is the URL for the settings subpage |sub_page|.
 bool IsSettingsSubPage(const GURL& url, const std::string& sub_page);
 
 // Returns true if |browser| is a trusted popup window containing a page with
 // matching |scheme| (or any trusted popup if |scheme| is empty).
 bool IsTrustedPopupWindowWithScheme(const Browser* browser,
                                     const std::string& scheme);
@@ skipping 26 matching lines @@
 
 // If the user is already signed in, shows the "Signin" portion of Settings,
 // otherwise initiates signin in a new browser tab.
 void ShowBrowserSigninOrSettings(Browser* browser,
                                  signin_metrics::AccessPoint access_point);
 #endif
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_UI_CHROME_PAGES_H_