Updated json_to_html to be sync.

tools/html_json_doc/lib/json_to_html.dart

 // Copyright (c) 2012, 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 for taking a JSON file and putting the comments located within into
  * the HTML files the comments are associated with.
  *
  * The format of the JSON file is:
  * 
@@ skipping 48 matching lines @@
     _anyErrors = true;
     completer.complete(false);
   } else {
     fileJson = JSON.parse(jsonRead);
   }
 
   // TODO(amouravski): Refactor to not duplicate code here and in html-to-json.
   // Find html files. (lister)
   final lister = htmlDir.list(recursive: false);
 
+  var pathList = <String>[];
   lister.onFile = (String path) {
+    pathList.add(path);
+  };
+
+  getFile(String path) {
     final name = new Path.fromNative(path).filename;
 
     // Ignore private classes.
     if (name.startsWith('_')) return;
 
     // Ignore non-dart files.
     if (!name.endsWith('.dart')) return;
 
     File file = new File(path);
 
@@ skipping 11 matching lines @@
     }
 
     var comments = fileJson[name];
 
     _convertFile(file, comments);
 
     fileJson.remove(name);
   };
 
   lister.onDone = (_) {
+    while(!pathList.isEmpty) {
+      getFile(pathList.removeLast());
+    }
 
     fileJson.forEach((key, _) {
       print('WARNING: the following filename was found in the JSON but not in '
           '${htmlDir.path}:\n"$key"');
       _anyErrors = true;
     });
 
     completer.complete(_anyErrors);
   };
 
@@ skipping 21 matching lines @@
     } else {
       unusedComments.putIfAbsent(key, () => comments);
     }
   });
 
   unusedComments.forEach((String key, _) {
     print('WARNING: the following key was found in the JSON but not in '
         '${new Path(file.fullPathSync()).filename}:\n"$key"');
     _anyErrors = true;
   });
-  
-  // TODO(amouravski): file.writeAsStringSync('${Strings.join(fileLines, '\n')}\n');
-  var outputStream = file.openOutputStream();
-  outputStream.writeString(Strings.join(fileLines, '\n'));
-  outputStream.writeString('\n');
 
-  outputStream.onNoPendingWrites = () {
-    outputStream.close();
-  };
+ file.writeAsStringSync('${Strings.join(fileLines, '\n')}\n');
 }