Avoid repeated declaration of the same loop variable.

lib/compiler/compiler.dart

Index: lib/compiler/compiler.dart
diff --git a/lib/compiler/compiler.dart b/lib/compiler/compiler.dart
index b7a780fe82600a5629e77f5890da41c3d79e9b02..4038fad3606ba13f5963af77807f6fcf7c9e30ca 100644
--- a/lib/compiler/compiler.dart
+++ b/lib/compiler/compiler.dart
@@ -46,7 +46,5 @@ Future<String> compile(Uri script,
                                    options);
   compiler.run(script);
   String code = compiler.assembledCode;
-  Completer<String> completer = new Completer<String>();
-  completer.complete(code);
-  return completer.future;
+  return new Future.immediate(code);
 }