small refactor: use JS.* prefix for our other JS extensions

lib/src/utils.dart

Index: lib/src/utils.dart
diff --git a/lib/src/utils.dart b/lib/src/utils.dart
index a3ea4fd10473e7e0ae5de4487e950caa7ca86071..1837b684905de08f9bc3d8d553f417043b11477d 100644
--- a/lib/src/utils.dart
+++ b/lib/src/utils.dart
@@ -31,7 +31,7 @@ import 'package:crypto/crypto.dart' show CryptoUtils, MD5;
 import 'package:source_span/source_span.dart';
 import 'package:yaml/yaml.dart';
 
-import 'codegen/js_names.dart' show invalidJSVariableName;
+import 'codegen/js_names.dart' show invalidVariableName;
 
 bool isDartPrivateLibrary(LibraryElement library) {
   var uri = library.source.uri;
@@ -69,7 +69,7 @@ String _toIdentifier(String name) {
   var result = buffer != null ? '$buffer' : name;
   // Ensure the identifier first character is not numeric and that the whole
   // identifier is not a keyword.
-  if (result.startsWith(new RegExp('[0-9]')) || invalidJSVariableName(result)) {
+  if (result.startsWith(new RegExp('[0-9]')) || invalidVariableName(result)) {
     return '\$$result';
   }
   return result;