Add dummy dart:html library for documentation.

lib/html/doc/interface/DirectoryEntry.dart

Index: lib/html/doc/interface/DirectoryEntry.dart
diff --git a/lib/html/doc/interface/DirectoryEntry.dart b/lib/html/doc/interface/DirectoryEntry.dart
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index 0000000000000000000000000000000000000000..a302a8c2a59098db3414880803c2b02d758d0be0
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+++ b/lib/html/doc/interface/DirectoryEntry.dart
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+// 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.
+
+// WARNING: Do not edit - generated code.
+
+/// @domName DirectoryEntry
+interface DirectoryEntry extends Entry {
+
+  /** @domName DirectoryEntry.createReader */
+  DirectoryReader createReader();
+
+  /** @domName DirectoryEntry.getDirectory */
+  void getDirectory(String path, [Object flags, EntryCallback successCallback, ErrorCallback errorCallback]);
+
+  /** @domName DirectoryEntry.getFile */
+  void getFile(String path, [Object flags, EntryCallback successCallback, ErrorCallback errorCallback]);
+
+  /** @domName DirectoryEntry.removeRecursively */
+  void removeRecursively(VoidCallback successCallback, [ErrorCallback errorCallback]);
+}