Add dummy dart:html library for documentation.

lib/html/doc/interface/SVGLength.dartdoc

+// 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:
+//   This file contains documentation that is merged into the real source.
+//   Do not make code changes here.
+
+/// @domName SVGLength
+interface SVGLength {
+
+  static final int SVG_LENGTHTYPE_CM = 6;
+
+  static final int SVG_LENGTHTYPE_EMS = 3;
+
+  static final int SVG_LENGTHTYPE_EXS = 4;
+
+  static final int SVG_LENGTHTYPE_IN = 8;
+
+  static final int SVG_LENGTHTYPE_MM = 7;
+
+  static final int SVG_LENGTHTYPE_NUMBER = 1;
+
+  static final int SVG_LENGTHTYPE_PC = 10;
+
+  static final int SVG_LENGTHTYPE_PERCENTAGE = 2;
+
+  static final int SVG_LENGTHTYPE_PT = 9;
+
+  static final int SVG_LENGTHTYPE_PX = 5;
+
+  static final int SVG_LENGTHTYPE_UNKNOWN = 0;
+
+  /** @domName SVGLength.unitType */
+  final int unitType;
+
+  /** @domName SVGLength.value */
+  num value;
+
+  /** @domName SVGLength.valueAsString */
+  String valueAsString;
+
+  /** @domName SVGLength.valueInSpecifiedUnits */
+  num valueInSpecifiedUnits;
+
+  /** @domName SVGLength.convertToSpecifiedUnits */
+  void convertToSpecifiedUnits(int unitType);
+
+  /** @domName SVGLength.newValueSpecifiedUnits */
+  void newValueSpecifiedUnits(int unitType, num valueInSpecifiedUnits);
+}