Add dummy dart:html library for documentation.

lib/html/doc/interface/SVGDocument.dart

Index: lib/html/doc/interface/SVGDocument.dart
diff --git a/lib/html/doc/interface/SVGDocument.dart b/lib/html/doc/interface/SVGDocument.dart
new file mode 100644
index 0000000000000000000000000000000000000000..4a1e0f49099e62232df06989c8fe4dd269e5d868
--- /dev/null
+++ b/lib/html/doc/interface/SVGDocument.dart
@@ -0,0 +1,15 @@
+// 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 SVGDocument
+interface SVGDocument extends Document {
+
+  /** @domName SVGDocument.rootElement */
+  final SVGSVGElement rootElement;
+
+  /** @domName SVGDocument.createEvent */
+  Event $dom_createEvent(String eventType);
+}