Add dummy dart:html library for documentation.

lib/html/doc/interface/RealtimeAnalyserNode.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 RealtimeAnalyserNode
+interface RealtimeAnalyserNode extends AudioNode {
+
+  /** @domName RealtimeAnalyserNode.fftSize */
+  int fftSize;
+
+  /** @domName RealtimeAnalyserNode.frequencyBinCount */
+  final int frequencyBinCount;
+
+  /** @domName RealtimeAnalyserNode.maxDecibels */
+  num maxDecibels;
+
+  /** @domName RealtimeAnalyserNode.minDecibels */
+  num minDecibels;
+
+  /** @domName RealtimeAnalyserNode.smoothingTimeConstant */
+  num smoothingTimeConstant;
+
+  /** @domName RealtimeAnalyserNode.getByteFrequencyData */
+  void getByteFrequencyData(Uint8Array array);
+
+  /** @domName RealtimeAnalyserNode.getByteTimeDomainData */
+  void getByteTimeDomainData(Uint8Array array);
+
+  /** @domName RealtimeAnalyserNode.getFloatFrequencyData */
+  void getFloatFrequencyData(Float32Array array);
+}