Turn on webaudio for JS backends.

client/dom/generated/src/frog/AudioContext.dart

Index: client/dom/generated/src/frog/AudioContext.dart
diff --git a/client/dom/generated/src/frog/AudioContext.dart b/client/dom/generated/src/frog/AudioContext.dart
new file mode 100644
index 0000000000000000000000000000000000000000..9de18b8d23efbe4a111470a332570e26acd7e773
--- /dev/null
+++ b/client/dom/generated/src/frog/AudioContext.dart
@@ -0,0 +1,49 @@
+
+class AudioContext native "*AudioContext" {
+
+  num currentTime;
+
+  AudioDestinationNode destination;
+
+  AudioListener listener;
+
+  num sampleRate;
+
+  RealtimeAnalyserNode createAnalyser() native;
+
+  BiquadFilterNode createBiquadFilter() native;
+
+  AudioBuffer createBuffer() native;
+
+  AudioBufferSourceNode createBufferSource() native;
+
+  AudioChannelMerger createChannelMerger() native;
+
+  AudioChannelSplitter createChannelSplitter() native;
+
+  ConvolverNode createConvolver() native;
+
+  DelayNode createDelayNode() native;
+
+  DynamicsCompressorNode createDynamicsCompressor() native;
+
+  AudioGainNode createGainNode() native;
+
+  HighPass2FilterNode createHighPass2Filter() native;
+
+  JavaScriptAudioNode createJavaScriptNode(int bufferSize) native;
+
+  LowPass2FilterNode createLowPass2Filter() native;
+
+  AudioPannerNode createPanner() native;
+
+  WaveShaperNode createWaveShaper() native;
+
+  void decodeAudioData(ArrayBuffer audioData, AudioBufferCallback successCallback, [AudioBufferCallback errorCallback = null]) native;
+
+  void startRendering() native;
+
+  var dartObjectLocalStorage;
+
+  String get typeName() native;
+}