Use dartfmt on Observatory code

runtime/observatory/web/main.dart

 // Copyright (c) 2014, 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.
 
 import 'dart:html';
 import 'package:logging/logging.dart';
 import 'package:observatory/elements.dart';
 import 'package:stack_trace/stack_trace.dart';
 
 main() async {
   Chain.capture(() async {
     Logger.root.level = Level.INFO;
     Logger.root.onRecord.listen((LogRecord rec) {
-        print('${rec.level.name}: ${rec.time}: ${rec.message}');
+      print('${rec.level.name}: ${rec.time}: ${rec.message}');
     });
     await initElements();
     Logger.root.info('Starting Observatory');
     document.body.children
         .insert(0, document.createElement('observatory-application'));
   });
 }