Fixed JS custom elements and temporarily mark polymer test as failing

tools/dom/templates/html/dartium/html_dartium.darttemplate

Index: tools/dom/templates/html/dartium/html_dartium.darttemplate
diff --git a/tools/dom/templates/html/dartium/html_dartium.darttemplate b/tools/dom/templates/html/dartium/html_dartium.darttemplate
index bb286402efe2af2cd13c1147b710fc85606c67dd..9bd24f0b78f54de6e6ea1ec344a701fb2b2698b2 100644
--- a/tools/dom/templates/html/dartium/html_dartium.darttemplate
+++ b/tools/dom/templates/html/dartium/html_dartium.darttemplate
@@ -355,6 +355,12 @@ Function _getSvgFunction(String key) {
 // List of known tagName to DartClass for custom elements, used for upgrade.
 var _knownCustomElements = new Map<String, Type>();
 
+void _addCustomElementType(String tagName, Type dartClass) {
+  _knownCustomElements[tagName] = dartClass;
+}
+
+Type _getCustomElementType(object) => _knownCustomElements[_getCustomElementName(object)];
+
 // Return the tag name or is attribute of the custom element or data binding.
 String _getCustomElementName(element) {
   var jsObject;
@@ -430,8 +436,7 @@ wrap_jso(jsObject) {
     if (wrapper != null) {
       if (wrapper.runtimeType == HtmlElement && !wrapper._isBadUpgrade) {
         // We're a Dart instance but we need to upgrade.
-        var tagName = _getCustomElementName(wrapper);
-        var customElementClass = _knownCustomElements[tagName];
+        var customElementClass = _getCustomElementType(wrapper);
         if (customElementClass != null) {
           var dartClass_instance;
           try {
@@ -483,8 +488,7 @@ wrap_jso(jsObject) {
       // make sure it's upgraded.
       dartClass_instance = _upgradeHtmlElement(jsObject['dart_class']);
     } else {
-      var tagName = _getCustomElementName(jsObject);
-      var customElementClass = _knownCustomElements[tagName];
+      var customElementClass = _getCustomElementType(jsObject);
       // Custom Element to upgrade.
       if (jsTypeName == 'HTMLElement' && customElementClass != null) {
         try {
@@ -503,6 +507,12 @@ wrap_jso(jsObject) {
         }
 
         var func = getHtmlCreateFunction(jsTypeName);
+        if (func == null) {
+          // One last ditch effort could be a JS custom element.
+          if (jsObject.toString() == "[object HTMLElement]") {
+            func = getHtmlCreateFunction("HTMLElement");
+          }
+        }
         if (func != null) {
           dartClass_instance = func();
           dartClass_instance.blink_jsObject = jsObject;
@@ -629,11 +639,12 @@ _upgradeHtmlElement(dartInstance) {
   // don't try it again - one failure is enough.
   if (dartInstance.runtimeType == HtmlElement && !dartInstance._isBadUpgrade) {
     // Must be exactly HtmlElement not something derived from it.
-    var jsObject = dartInstance.blink_jsObject;
-    var tagName = _getCustomElementName(dartInstance);
-    var customElementClass = _knownCustomElements[tagName];
+
+    var customElementClass = _getCustomElementType(dartInstance);
+
     // Custom Element to upgrade.
     if (customElementClass != null) {
+      var jsObject = dartInstance.blink_jsObject;
       try {
         dartInstance = _blink.Blink_Utils.constructElement(customElementClass, jsObject);
       } catch (e) {