Add initial implementation of date-time-settings MD settings page.

chrome/browser/resources/settings/pref_tracker/pref_tracker.js

Index: chrome/browser/resources/settings/pref_tracker/pref_tracker.js
diff --git a/chrome/browser/resources/settings/pref_tracker/pref_tracker.js b/chrome/browser/resources/settings/pref_tracker/pref_tracker.js
index 104b18626e8f9cabb4ca0f390208ae50bcea8a5c..29fa6ef22cab39776fe2ed96d42f019e0c02269e 100644
--- a/chrome/browser/resources/settings/pref_tracker/pref_tracker.js
+++ b/chrome/browser/resources/settings/pref_tracker/pref_tracker.js
@@ -74,7 +74,7 @@
           var parentPrefString = this.parentNode && this.parentNode.host &&
               this.parentNode.host.getAttribute('pref');
           if (parentPrefString) {
-            keyHint = parentPrefString.match(/{{([a-z._]+)}}/)[1];
+            keyHint = parentPrefString.match(/{{([a-z0-9._]+)}}/)[1];
           }
 
           throw new Error('Pref not found. Key Hint: ' + keyHint);