Some cleanups to Frog to avoid looking up its builtin types too much

frog/type.dart

Index: frog/type.dart
diff --git a/frog/type.dart b/frog/type.dart
index 9f612b73c7dafab2ff0ae27db60dde90fafa48b0..677c8b29456bb90b0d5e6c7e8861fd3b3602b3a8 100644
--- a/frog/type.dart
+++ b/frog/type.dart
@@ -107,8 +107,8 @@ class Type extends Element {
 
   Map<String, Member> getAllMembers() => {};
 
-  /** The native name of this element if it has one. */
-  String get nativeName() => isNative ? definition.nativeType.name : null;
+  /** The native name of this element if it has one, otherwise the JS name. */
+  String get nativeName() => isNative ? definition.nativeType.name : jsname;
 
   /**
    * Avoid the native name if hidden native. It might exist on some browsers and