Partially rollback noSuchMethod for UnknownElement until we figure out code size issue

lib/html/dart2js/html_dart2js.dart

Index: lib/html/dart2js/html_dart2js.dart
diff --git a/lib/html/dart2js/html_dart2js.dart b/lib/html/dart2js/html_dart2js.dart
index d35178dc66ce7dc4962ef21d142f16f950f52948..ba2ab82808f841116b3865f285d496794cf3b82f 100644
--- a/lib/html/dart2js/html_dart2js.dart
+++ b/lib/html/dart2js/html_dart2js.dart
@@ -15328,13 +15328,7 @@ class _UnknownElementImpl extends _ElementImpl implements UnknownElement native
   // Hooks to support custom WebComponents.
   var xtag;
 
-  noSuchMethod(String name, List args) {
-    if (dynamicUnknownElementDispatcher == null) {
-      throw new NoSuchMethodException(this, name, args);
-    } else {
-      return dynamicUnknownElementDispatcher(this, name, args);
-    }
-  }
+  // TODO(vsm): Implement noSuchMethod or similar for dart2js.
 }
 
 class _ValidityStateImpl implements ValidityState native "*ValidityState" {