Make dart:dom implementation types private so they don't muddle the docs.

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

Index: client/dom/generated/src/frog/AudioPannerNode.dart
diff --git a/client/dom/generated/src/frog/AudioPannerNode.dart b/client/dom/generated/src/frog/AudioPannerNode.dart
index ce202167fc5c2cb2c9ca8efb58b3d38190d48fea..5a50097b43e44d1382644b842ef1d142b28a6606 100644
--- a/client/dom/generated/src/frog/AudioPannerNode.dart
+++ b/client/dom/generated/src/frog/AudioPannerNode.dart
@@ -1,5 +1,5 @@
 
-class AudioPannerNodeJs extends AudioNodeJs implements AudioPannerNode native "*AudioPannerNode" {
+class _AudioPannerNodeJs extends _AudioNodeJs implements AudioPannerNode native "*AudioPannerNode" {
 
   static final int EQUALPOWER = 0;
 
@@ -7,7 +7,7 @@ class AudioPannerNodeJs extends AudioNodeJs implements AudioPannerNode native "*
 
   static final int SOUNDFIELD = 2;
 
-  AudioGainJs get coneGain() native "return this.coneGain;";
+  _AudioGainJs get coneGain() native "return this.coneGain;";
 
   num get coneInnerAngle() native "return this.coneInnerAngle;";
 
@@ -21,7 +21,7 @@ class AudioPannerNodeJs extends AudioNodeJs implements AudioPannerNode native "*
 
   void set coneOuterGain(num value) native "this.coneOuterGain = value;";
 
-  AudioGainJs get distanceGain() native "return this.distanceGain;";
+  _AudioGainJs get distanceGain() native "return this.distanceGain;";
 
   int get distanceModel() native "return this.distanceModel;";