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

tracing/tracing/ui/tracks/process_memory_dump_track_test.html

Index: tracing/tracing/ui/tracks/process_memory_dump_track_test.html
diff --git a/tracing/tracing/ui/tracks/process_memory_dump_track_test.html b/tracing/tracing/ui/tracks/process_memory_dump_track_test.html
index a4515d504033e4e045f6b2b7bb6d7529740fd9a0..4692525b9dcf62c16f9f5e7b8846f37d0b3a55f8 100644
--- a/tracing/tracing/ui/tracks/process_memory_dump_track_test.html
+++ b/tracing/tracing/ui/tracks/process_memory_dump_track_test.html
@@ -26,10 +26,10 @@ tr.b.unittest.testSuite(function() {
     var div = document.createElement('div');
     var viewport = new Viewport(div);
     var drawingContainer = new tr.ui.tracks.DrawingContainer(viewport);
-    div.appendChild(drawingContainer);
+    Polymer.dom(div).appendChild(drawingContainer);
 
     var track = new ProcessMemoryDumpTrack(viewport);
-    drawingContainer.appendChild(track);
+    Polymer.dom(drawingContainer).appendChild(track);
     drawingContainer.invalidate();
 
     track.memoryDumps = dumps;