Use Polymer.dom with many dom manipulations.

tracing/tracing/ui/base/table_test.html

Index: tracing/tracing/ui/base/table_test.html
diff --git a/tracing/tracing/ui/base/table_test.html b/tracing/tracing/ui/base/table_test.html
index 5487d436c2ba71543663037fa74a335c1c138979..b4802fde7973a1ce7b9db617b7b3e7ad652537b0 100644
--- a/tracing/tracing/ui/base/table_test.html
+++ b/tracing/tracing/ui/base/table_test.html
@@ -384,7 +384,8 @@ tr.b.unittest.testSuite(function() {
         });
     assert.isDefined(bToplevelEl);
     var expandButton = bToplevelEl.parentElement.querySelector('expand-button');
-    assert.isTrue(expandButton.classList.contains('button-expanded'));
+    assert.isTrue(Polymer.dom(expandButton).classList.contains(
+        'button-expanded'));
   });
 
 
@@ -1239,7 +1240,7 @@ tr.b.unittest.testSuite(function() {
     this.addHTMLOutput(table);
 
     // check that we don't have 'undefined' anywhere
-    assert.isTrue(table.$.body.innerHTML.indexOf('undefined') < 0);
+    assert.isTrue(Polymer.dom(table.$.body).innerHTML.indexOf('undefined') < 0);
   });
 
   test('customizeTableRowCallback', function() {