MD Settings: Remove some ES6 leftovers from CrOS code that break uglify.

chrome/browser/resources/settings/people_page/camera.js

Index: chrome/browser/resources/settings/people_page/camera.js
diff --git a/chrome/browser/resources/settings/people_page/camera.js b/chrome/browser/resources/settings/people_page/camera.js
index e31a25d171138d2cbd00561b7ca1c31f4eb2810a..ce25918758c058ee147874f3ea0dfd43c5274d34 100644
--- a/chrome/browser/resources/settings/people_page/camera.js
+++ b/chrome/browser/resources/settings/people_page/camera.js
@@ -141,8 +141,8 @@ Polymer({
    */
   stopVideoTracks_: function(stream) {
     var tracks = stream.getVideoTracks();
-    for (var t of tracks)
-      t.stop();
+    for (var i = 0; i < tracks.length; i++)
+      tracks[i].stop();
   },
 
   /**