[polymer] Switches .appendChild() to Polymer.dom()...appendChild()

tracing/tracing/trace2html.html

Index: tracing/tracing/trace2html.html
diff --git a/tracing/tracing/trace2html.html b/tracing/tracing/trace2html.html
index 05790b5e6767b6ef25c16a6a1fba393e78292c9e..ba6b953b2944c6110584ae5fd56efa964814eb92 100644
--- a/tracing/tracing/trace2html.html
+++ b/tracing/tracing/trace2html.html
@@ -31,7 +31,7 @@ var g_timelineViewEl;
     '}'
   ];
   styleEl.textContent = lines.join('\n');
-  document.head.appendChild(styleEl);
+  Polymer.dom(document.head).appendChild(styleEl);
 })();
 
 document.addEventListener('DOMContentLoaded', function() {
@@ -39,9 +39,9 @@ document.addEventListener('DOMContentLoaded', function() {
   container.id = 'track_view_container';
 
   g_timelineViewEl = document.createElement('tr-ui-timeline-view');
-  g_timelineViewEl.appendChild(container);
+  Polymer.dom(g_timelineViewEl).appendChild(container);
 
-  document.body.appendChild(g_timelineViewEl);
+  Polymer.dom(document.body).appendChild(g_timelineViewEl);
 
   var traces = [];
   var viewerDataScripts = document.querySelectorAll('#viewer-data');