Add dummy dart:html library for documentation.

lib/html/doc/interface/AudioParam.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 AudioParam
+interface AudioParam {
+
+  /** @domName AudioParam.defaultValue */
+  final num defaultValue;
+
+  /** @domName AudioParam.maxValue */
+  final num maxValue;
+
+  /** @domName AudioParam.minValue */
+  final num minValue;
+
+  /** @domName AudioParam.name */
+  final String name;
+
+  /** @domName AudioParam.units */
+  final int units;
+
+  /** @domName AudioParam.value */
+  num value;
+
+  /** @domName AudioParam.cancelScheduledValues */
+  void cancelScheduledValues(num startTime);
+
+  /** @domName AudioParam.exponentialRampToValueAtTime */
+  void exponentialRampToValueAtTime(num value, num time);
+
+  /** @domName AudioParam.linearRampToValueAtTime */
+  void linearRampToValueAtTime(num value, num time);
+
+  /** @domName AudioParam.setTargetValueAtTime */
+  void setTargetValueAtTime(num targetValue, num time, num timeConstant);
+
+  /** @domName AudioParam.setValueAtTime */
+  void setValueAtTime(num value, num time);
+
+  /** @domName AudioParam.setValueCurveAtTime */
+  void setValueCurveAtTime(Float32Array values, num time, num duration);
+}