Add dummy dart:html library for documentation.

lib/html/doc/interface/SpeechGrammarList.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.
+
+// WARNING: Do not edit - generated code.
+
+/// @domName SpeechGrammarList
+interface SpeechGrammarList default _SpeechGrammarListFactoryProvider {
+
+  SpeechGrammarList();
+
+  /** @domName SpeechGrammarList.length */
+  final int length;
+
+  /** @domName SpeechGrammarList.addFromString */
+  void addFromString(String string, [num weight]);
+
+  /** @domName SpeechGrammarList.addFromUri */
+  void addFromUri(String src, [num weight]);
+
+  /** @domName SpeechGrammarList.item */
+  SpeechGrammar item(int index);
+}