[CrOS Settings] Fix time displayed format for night slider settings.

The navigator.language must be explicitly passed into the time
formatter for ES-419 formatted time to be displayed. This also
corrects the additional zero shown in single digit hours.

Bug: 1076309
Change-Id: Idd09e744e72a5d0cbaaa1ec92e4d1b88a8683105
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2250473Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Regan Hsu <hsuregan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#779691}

chrome/browser/resources/settings/chromeos/device_page/night_light_slider.js

@@ -320,7 +320,8 @@ Polymer({
     d.setMilliseconds(0);
 
     return d.toLocaleTimeString(
-        [], {hour: '2-digit', minute: '2-digit', hour12: !shouldUse24Hours});
+        navigator.language,
+        {hour: 'numeric', minute: 'numeric', hour12: !shouldUse24Hours});
   },
 
   /**