Avoid repeated declaration of the same loop variable.

lib/compiler/compiler.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #library('compiler');
 
 #import('dart:uri');
 #import('implementation/apiimpl.dart');
 
 // Unless explicitly allowed, passing null for any argument to the
@@ skipping 28 matching lines @@
 Future<String> compile(Uri script,
                        Uri libraryRoot,
                        Uri packageRoot,
                        ReadUriFromString provider,
                        DiagnosticHandler handler,
                        [List<String> options = const []]) {
   Compiler compiler = new Compiler(provider, handler, libraryRoot, packageRoot,
                                    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);
 }