[polymer] Fix missing $ in value set view

tracing/tracing/value/ui/value_set_view.html

Index: tracing/tracing/value/ui/value_set_view.html
diff --git a/tracing/tracing/value/ui/value_set_view.html b/tracing/tracing/value/ui/value_set_view.html
index 8c8b30e6d248ccb6d91417c656b653b3364c2ec3..dec79acb17da9318d1fdce8f7059d8776aef1bcf 100644
--- a/tracing/tracing/value/ui/value_set_view.html
+++ b/tracing/tracing/value/ui/value_set_view.html
@@ -230,7 +230,7 @@ tr.exportTo('tr.v.ui', function() {
 
       // TODO(charliea): If TabView were structured correctly, this could almost
       // certainly be done with attribute binding in the HTML template.
-      this.$.tabView.set('tabsHidden', this$.tabView.tabs.length === 1);
+      this.$.tabView.set('tabsHidden', this.$.tabView.tabs.length === 1);
     }
   });