Native wrappers should implement dart:html interfaces.

lib/dom/templates/dom/native/dart_implementation.darttemplate

Index: lib/dom/templates/dom/native/dart_implementation.darttemplate
diff --git a/lib/dom/templates/dom/native/dart_implementation.darttemplate b/lib/dom/templates/dom/native/dart_implementation.darttemplate
index 23e7d6f7b6206314f906707727bd9b6d648374f3..2b1cfaf51f53f4b2f59e782c72cef701c9ec0a51 100644
--- a/lib/dom/templates/dom/native/dart_implementation.darttemplate
+++ b/lib/dom/templates/dom/native/dart_implementation.darttemplate
@@ -4,10 +4,7 @@
 
 // WARNING: Do not edit - generated code.
 
-interface _$INTERFACE {
-}
-
-class $CLASS extends $BASE implements _$INTERFACE {
+class $CLASS extends $BASE implements $HTML_INTERFACE {
   $CLASS();
   String get typeName() => "$INTERFACE";
 $MEMBERS