dart2js: run dartfmt on tests

tests/compiler/dart2js/mirror_tree_shaking_test.dart

 // Copyright (c) 2013, 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.
 
 // Test that tree-shaking hasn't been turned off.
 
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/compiler.dart';
-import 'package:compiler/src/js_backend/js_backend.dart'
-       show JavaScriptBackend;
+import 'package:compiler/src/js_backend/js_backend.dart' show JavaScriptBackend;
 import 'package:expect/expect.dart';
 import 'memory_compiler.dart';
 
 main() {
   DiagnosticCollector collector = new DiagnosticCollector();
   asyncTest(() async {
     CompilationResult result = await runCompiler(
-      memorySourceFiles: MEMORY_SOURCE_FILES, diagnosticHandler: collector);
+        memorySourceFiles: MEMORY_SOURCE_FILES, diagnosticHandler: collector);
     Compiler compiler = result.compiler;
     Expect.isTrue(collector.errors.isEmpty);
     Expect.isTrue(collector.infos.isEmpty);
     Expect.isFalse(compiler.compilationFailed);
     Expect.isFalse(compiler.enqueuer.resolution.hasEnqueuedReflectiveElements);
     Expect.isFalse(
         compiler.enqueuer.resolution.hasEnqueuedReflectiveStaticFields);
     JavaScriptBackend backend = compiler.backend;
     Expect.isFalse(backend.codegenEnqueuer.hasEnqueuedReflectiveElements);
     Expect.isFalse(backend.codegenEnqueuer.hasEnqueuedReflectiveStaticFields);
@@ skipping 11 matching lines @@
     print('Invoked ${MirrorSystem.getName(invocation.memberName)}');
     return reflect('foobar').delegate(invocation);
   }
 }
 
 void main() {
   print(new Foo().substring(3));
 }
 """,
 };