Provide source map info for simple async methods.

tests/compiler/dart2js/sourcemaps/output_structure.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.
 
 library sourcemap.output_structure;
 
 import 'dart:math' as Math;
 import 'html_parts.dart' show Annotation, CodeLine, JsonStrategy;
 
 // Constants used to identify the subsection of the JavaScript output. These
@@ skipping 619 matching lines @@
     return new Interval(Math.min(from, index), Math.max(to, index + 1));
   }
 
   bool inWindow(int index, {int windowSize: 0}) {
     return from - windowSize <= index && index < to + windowSize;
   }
 
   String toString() => '[$from,$to[';
 }
 
-enum CodeKind {
-  LIBRARY,
-  CLASS,
-  MEMBER,
-}
+enum CodeKind { LIBRARY, CLASS, MEMBER, }
 
 class CodeLocation {
   final Uri uri;
   final String name;
   final int offset;
 
   CodeLocation(this.uri, this.name, this.offset);
 
   String toString() => '$uri:$name:$offset';
 
@@ skipping 54 matching lines @@
   }
 
   static CodeSource fromJson(Map json) {
     if (json == null) return null;
     CodeSource codeSource = new CodeSource(CodeKind.values[json['kind']],
         Uri.parse(json['uri']), json['name'], json['begin'], json['end']);
     json['members'].forEach((m) => codeSource.members.add(fromJson(m)));
     return codeSource;
   }
 }