Change List.sort to not have a default parameter value.

sdk/lib/html/templates/html/impl/impl_Element.darttemplate

Index: sdk/lib/html/templates/html/impl/impl_Element.darttemplate
diff --git a/sdk/lib/html/templates/html/impl/impl_Element.darttemplate b/sdk/lib/html/templates/html/impl/impl_Element.darttemplate
index cd532c5c838f73efbb83228b1c745598b21df45e..e01e3713df1d7ccbb375aabda62b8d915e7ba771 100644
--- a/sdk/lib/html/templates/html/impl/impl_Element.darttemplate
+++ b/sdk/lib/html/templates/html/impl/impl_Element.darttemplate
@@ -103,7 +103,7 @@ class _ChildrenElementList implements List {
     }
   }
 
-  void sort([Comparator<Element> compare = Comparable.compare]) {
+  void sort([int compare(Element a, Element b)]) {
     throw new UnsupportedError('TODO(jacobr): should we impl?');
   }
 
@@ -239,7 +239,7 @@ class _FrozenElementList implements List {
     throw new UnsupportedError('');
   }
 
-  void sort([Comparator<Element> compare = Comparable.compare]) {
+  void sort([int compare(Element a, Element b)]) {
     throw new UnsupportedError('');
   }