Add dummy dart:html library for documentation.

lib/html/doc/interface/SVGPathSegCurvetoCubicSmoothRel.dart

Index: lib/html/doc/interface/SVGPathSegCurvetoCubicSmoothRel.dart
diff --git a/lib/html/doc/interface/SVGPathSegCurvetoCubicSmoothRel.dart b/lib/html/doc/interface/SVGPathSegCurvetoCubicSmoothRel.dart
new file mode 100644
index 0000000000000000000000000000000000000000..6cc8fa1db88f480b25144b83f559384ecc08267d
--- /dev/null
+++ b/lib/html/doc/interface/SVGPathSegCurvetoCubicSmoothRel.dart
@@ -0,0 +1,21 @@
+// 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 SVGPathSegCurvetoCubicSmoothRel
+interface SVGPathSegCurvetoCubicSmoothRel extends SVGPathSeg {
+
+  /** @domName SVGPathSegCurvetoCubicSmoothRel.x */
+  num x;
+
+  /** @domName SVGPathSegCurvetoCubicSmoothRel.x2 */
+  num x2;
+
+  /** @domName SVGPathSegCurvetoCubicSmoothRel.y */
+  num y;
+
+  /** @domName SVGPathSegCurvetoCubicSmoothRel.y2 */
+  num y2;
+}