Further reduce use of Element in codegen.

pkg/compiler/lib/src/js_backend/namer.dart

Index: pkg/compiler/lib/src/js_backend/namer.dart
diff --git a/pkg/compiler/lib/src/js_backend/namer.dart b/pkg/compiler/lib/src/js_backend/namer.dart
index 717cbc630a95d6d39464d8d2fbe0ebc0ce8a4abb..c2e7b4d1acb9ba1e31662a78af36025e6d591e65 100644
--- a/pkg/compiler/lib/src/js_backend/namer.dart
+++ b/pkg/compiler/lib/src/js_backend/namer.dart
@@ -1369,7 +1369,7 @@ class Namer {
   ///         this.super$A$foo(); // super.foo()
   ///     }
   ///
-  jsAst.Name aliasedSuperMemberPropertyName(Element member) {
+  jsAst.Name aliasedSuperMemberPropertyName(MemberElement member) {
     assert(!member.isField); // Fields do not need super aliases.
     return _disambiguateInternalMember(member, () {
       String invocationName = operatorNameToIdentifier(member.name);