Remove DirectoryException and LinkException from dart:io and use FileException instaed.

sdk/lib/_internal/dartdoc/lib/dartdoc.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.
 
 /**
  * To generate docs for a library, run this script with the path to an
  * entrypoint .dart file, like:
  *
  *     $ dart dartdoc.dart foo.dart
  *
@@ skipping 589 matching lines @@
 
   void endFile() {
     final outPath = path.join(outputDir, _filePath);
     final dir = new Directory(path.dirname(outPath));
     if (!dir.existsSync()) {
       // TODO(3914): Hack to avoid 'file already exists' exception
       // thrown due to invalid result from dir.existsSync() (probably due to
       // race conditions).
       try {
         dir.createSync();
-      } on DirectoryException catch (e) {
+      } on FileSystemException catch (e) {
         // Ignore.
       }
     }
 
     writeString(new File(outPath), _file.toString());
     _filePath = null;
     _file = null;
   }
 
   void write(String s) {
@@ skipping 1691 matching lines @@
    return '''
         <div class="mdn">
         $mdnComment
         <div class="mdn-note"><a href="$mdnUrl">from MDN</a></div>
         </div>
         ''';
   }
 
   String toString() => mdnComment;
 }