Use dartfmt on Observatory code

runtime/observatory/lib/src/elements/nav/library_menu.dart

 // Copyright (c) 2016, 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 IsolateRef, LibraryRef;
 import 'package:observatory/src/elements/helpers/nav_menu.dart';
 import 'package:observatory/src/elements/helpers/rendering_scheduler.dart';
 import 'package:observatory/src/elements/helpers/tag.dart';
@@ skipping 40 matching lines @@
 
   @override
   void detached() {
     super.detached();
     children = [];
     _r.disable(notify: true);
   }
 
   void render() {
     children = [
-      navMenu(library.name, content: _content,
-                link: Uris.inspect(isolate, object: library).toString())
+      navMenu(library.name,
+          content: _content,
+          link: Uris.inspect(isolate, object: library).toString())
     ];
   }
 }