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

chrome/common/url_constants.cc

Index: chrome/common/url_constants.cc
diff --git a/chrome/common/url_constants.cc b/chrome/common/url_constants.cc
index 68c305a5fa22b8f034dd301808f1542a45ea4761..26b14b958212a6a023f9e2b6e541b02e7b5bfa0e 100644
--- a/chrome/common/url_constants.cc
+++ b/chrome/common/url_constants.cc
@@ -79,6 +79,7 @@ const char kChromeUIPrintURL[] = "chrome://print/";
 const char kChromeUIQuitURL[] = "chrome://quit/";
 const char kChromeUIRestartURL[] = "chrome://restart/";
 const char kChromeUISettingsURL[] = "chrome://settings/";
+const char kChromeUISettingsLegacyURL[] = "chrome://settings/";
 const char kChromeUIContentSettingsURL[] = "chrome://settings/content";
 const char kChromeUISettingsFrameURL[] = "chrome://settings-frame/";
 const char kChromeUISuggestionsURL[] = "chrome://suggestions/";
@@ -228,6 +229,7 @@ const char kChromeUIProfilerHost[] = "profiler";
 const char kChromeUIQuotaInternalsHost[] = "quota-internals";
 const char kChromeUIQuitHost[] = "quit";
 const char kChromeUIRestartHost[] = "restart";
+const char kChromeUISettingsLegacyHost[] = "legacy-settings";
 const char kChromeUISettingsHost[] = "settings";
 const char kChromeUISettingsFrameHost[] = "settings-frame";
 const char kChromeUIShorthangHost[] = "shorthang";