[polymer] Replaces this.appendChild with Polymer.dom(this).appendChild

tracing/tracing/ui/tracks/kernel_track.html

Index: tracing/tracing/ui/tracks/kernel_track.html
diff --git a/tracing/tracing/ui/tracks/kernel_track.html b/tracing/tracing/ui/tracks/kernel_track.html
index 20ffea84d053fae15e2f2336523bb89e80f6e8a0..45f95033f1630092fa5afa7a2378dbcf4781ceac 100644
--- a/tracing/tracing/ui/tracks/kernel_track.html
+++ b/tracing/tracing/ui/tracks/kernel_track.html
@@ -66,11 +66,11 @@ tr.exportTo('tr.ui.tracks', function() {
         track.cpu = cpu;
         if (!track.hasVisibleContent)
           continue;
-        this.appendChild(track);
+        Polymer.dom(this).appendChild(track);
         didAppendAtLeastOneTrack = true;
       }
       if (didAppendAtLeastOneTrack)
-        this.appendChild(new SpacingTrack(this.viewport));
+        Polymer.dom(this).appendChild(new SpacingTrack(this.viewport));
     }
   };