Use dartfmt on Observatory code

runtime/observatory/lib/src/elements/sentinel_value.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.
 
 import 'dart:html';
 import 'dart:async';
 import 'package:observatory/models.dart' as M show Sentinel, SentinelKind;
 import 'package:observatory/src/elements/helpers/rendering_scheduler.dart';
 import 'package:observatory/src/elements/helpers/tag.dart';
 
@@ skipping 36 matching lines @@
     text = _sentinel.valueAsString;
     title = _sentinelKindToDescription(_sentinel.kind);
   }
 
   static String _sentinelKindToDescription(M.SentinelKind kind) {
     switch (kind) {
       case M.SentinelKind.collected:
         return 'This object has been reclaimed by the garbage collector.';
       case M.SentinelKind.expired:
         return 'The handle to this object has expired. '
-               'Consider refreshing the page.';
+            'Consider refreshing the page.';
       case M.SentinelKind.notInitialized:
         return 'This object will be initialized once it is accessed by '
-               'the program.';
+            'the program.';
       case M.SentinelKind.initializing:
         return 'This object is currently being initialized.';
       case M.SentinelKind.optimizedOut:
         return 'This object is no longer needed and has been removed by the '
-               'optimizing compiler.';
+            'optimizing compiler.';
       case M.SentinelKind.free:
         return '';
     }
     throw new Exception('Unknown SentinelKind: $kind');
   }
-
 }