Add dummy dart:html library for documentation.

lib/html/doc/interface/WebGLVertexArrayObjectOES.dart

Index: lib/html/doc/interface/WebGLVertexArrayObjectOES.dart
diff --git a/lib/html/doc/interface/WebGLVertexArrayObjectOES.dart b/lib/html/doc/interface/WebGLVertexArrayObjectOES.dart
new file mode 100644
index 0000000000000000000000000000000000000000..c5227ac8e24058e43a4a87ae9015eb8fc0efcff0
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+++ b/lib/html/doc/interface/WebGLVertexArrayObjectOES.dart
@@ -0,0 +1,9 @@
+// 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 WebGLVertexArrayObjectOES
+interface WebGLVertexArrayObjectOES {
+}