Use fields in hidden native DOM classes instead of getters/setters.

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

Index: client/dom/generated/src/frog/AudioBuffer.dart
diff --git a/client/dom/generated/src/frog/AudioBuffer.dart b/client/dom/generated/src/frog/AudioBuffer.dart
index cbef53f65e46b26fbac35753baa0021ae9c6c9ad..05ff60c40caf4ab4e4b8adf405cf52a36693b650 100644
--- a/client/dom/generated/src/frog/AudioBuffer.dart
+++ b/client/dom/generated/src/frog/AudioBuffer.dart
@@ -1,17 +1,15 @@
 
 class _AudioBufferJs extends _DOMTypeJs implements AudioBuffer native "*AudioBuffer" {
 
-  num get duration() native "return this.duration;";
+  final num duration;
 
-  num get gain() native "return this.gain;";
+  num gain;
 
-  void set gain(num value) native "this.gain = value;";
+  final int length;
 
-  int get length() native "return this.length;";
+  final int numberOfChannels;
 
-  int get numberOfChannels() native "return this.numberOfChannels;";
-
-  num get sampleRate() native "return this.sampleRate;";
+  final num sampleRate;
 
   _Float32ArrayJs getChannelData(int channelIndex) native;
 }