More tests now pass and fixed custom elements to only work in default html and svg namespace

sdk/lib/html/dartium/html_dartium.dart

Index: sdk/lib/html/dartium/html_dartium.dart
diff --git a/sdk/lib/html/dartium/html_dartium.dart b/sdk/lib/html/dartium/html_dartium.dart
index a4d3eb755b61d0b3ac9a44b42ab3225d92542bc8..1f9f0249c529ff39b5b82b67c3128ab37ad7d945 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -1219,7 +1219,7 @@ class DartHtmlDomObject {
 
 // Flag to disable JS interop asserts.  Setting to false will speed up the
 // wrap_jso calls.
-bool __interop_checks = true;
+bool __interop_checks = false;
 
 /** Expando for JsObject, used by every Dart class associated with a Javascript
  *  class (e.g., DOM, WebAudio, etc.).
@@ -1304,7 +1304,11 @@ wrap_jso(jsObject) {
     }
 
     // Custom Element to upgrade.
-    if (customElementClass != null && extendsTag == "") {
+    // Only allow custome elements to be created in the html or svg default
+    // namespace.
+    var defaultNS = jsObject['namespaceURI'] == 'http://www.w3.org/1999/xhtml' ||
+        jsObject['namespaceURI'] ==  'http://www.w3.org/2000/svg';
+    if (customElementClass != null && extendsTag == "" && defaultNS) {
       try {
         dartClass_instance = _blink.Blink_Utils.constructElement(customElementClass, jsObject);
       } finally {