Use Polymer.dom with many dom manipulations.

tracing/tracing/value/ui/scalar_span.html

Index: tracing/tracing/value/ui/scalar_span.html
diff --git a/tracing/tracing/value/ui/scalar_span.html b/tracing/tracing/value/ui/scalar_span.html
index aea5ec7b63d94f447346a4e3042be41f0740bc68..f60f14b20202840e80138342f392c1cd3a8e9940 100644
--- a/tracing/tracing/value/ui/scalar_span.html
+++ b/tracing/tracing/value/ui/scalar_span.html
@@ -151,14 +151,14 @@ Polymer({
   },
 
   get rightAlign() {
-    return this.$.content.classList.contains('right-align');
+    return Polymer.dom(this.$.content).classList.contains('right-align');
   },
 
   set rightAlign(rightAlign) {
     if (rightAlign)
-      this.$.content.classList.add('right-align');
+      Polymer.dom(this.$.content).classList.add('right-align');
     else
-      this.$.content.classList.remove('right-align');
+      Polymer.dom(this.$.content).classList.remove('right-align');
   },
 
   updateSparkline_: function() {