Turn on webaudio for JS backends.

client/dom/generated/src/wrapping/_AudioGainNodeWrappingImplementation.dart

+// Copyright (c) 2011, 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.
+
+class _AudioGainNodeWrappingImplementation extends _AudioNodeWrappingImplementation implements AudioGainNode {
+  _AudioGainNodeWrappingImplementation() : super() {}
+
+  static create__AudioGainNodeWrappingImplementation() native {
+    return new _AudioGainNodeWrappingImplementation();
+  }
+
+  AudioGain get gain() { return _get_gain(this); }
+  static AudioGain _get_gain(var _this) native;
+
+  String get typeName() { return "AudioGainNode"; }
+}