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

chrome/browser/browser_about_handler.cc

Index: chrome/browser/browser_about_handler.cc
diff --git a/chrome/browser/browser_about_handler.cc b/chrome/browser/browser_about_handler.cc
index 04274b19630444720285912579e02d40cfcc37a8..a6a829f8ca5b274786777288e446491ff162c923 100644
--- a/chrome/browser/browser_about_handler.cc
+++ b/chrome/browser/browser_about_handler.cc
@@ -92,6 +92,9 @@ bool WillHandleBrowserAboutURL(GURL* url,
   } else if (host == chrome::kChromeUISettingsHost) {
     if (::switches::AboutInSettingsEnabled()) {
       host = chrome::kChromeUISettingsFrameHost;
+    } else if (base::FeatureList::IsEnabled(
+                   features::kMaterialDesignSettingsFeature)) {
+      // No rewrite in this case.
     } else {

[Dan Beam, 2016/06/01 20:54:50]

can't this just be:

} else if (!base::FeatureList::IsEnabled(
                features::kMaterialDesignSettingsFeature)) {
  host = chrome::kChromeUIUberHost;
  path = chrome::kChromeUISettingsHost + url->path();
}

[groby-ooo-7-16, 2016/06/02 23:03:53]

I kind of like explicitly calling out the alternatives - so I called it out in
the comments :) (Done)

       host = chrome::kChromeUIUberHost;
       path = chrome::kChromeUISettingsHost + url->path();
@@ -102,6 +105,8 @@ bool WillHandleBrowserAboutURL(GURL* url,
       host = chrome::kChromeUISettingsFrameHost;
       if (url->path().empty() || url->path() == "/")
         path = chrome::kChromeUIHelpHost;
+    } else if (base::FeatureList::IsEnabled(
+                   features::kMaterialDesignSettingsFeature)) {

[Dan Beam, 2016/06/01 20:54:50]

same

[groby-ooo-7-16, 2016/06/02 23:03:53]

Done.

     } else {
       host = chrome::kChromeUIUberHost;
       path = chrome::kChromeUIHelpHost + url->path();