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

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

 
-class WebGLContextAttributesJs extends DOMTypeJs implements WebGLContextAttributes native "*WebGLContextAttributes" {
+class _WebGLContextAttributesJs extends _DOMTypeJs implements WebGLContextAttributes native "*WebGLContextAttributes" {
 
   bool get alpha() native "return this.alpha;";
 
   void set alpha(bool value) native "this.alpha = value;";
 
   bool get antialias() native "return this.antialias;";
 
   void set antialias(bool value) native "this.antialias = value;";
 
   bool get depth() native "return this.depth;";
 
   void set depth(bool value) native "this.depth = value;";
 
   bool get premultipliedAlpha() native "return this.premultipliedAlpha;";
 
   void set premultipliedAlpha(bool value) native "this.premultipliedAlpha = value;";
 
   bool get preserveDrawingBuffer() native "return this.preserveDrawingBuffer;";
 
   void set preserveDrawingBuffer(bool value) native "this.preserveDrawingBuffer = value;";
 
   bool get stencil() native "return this.stencil;";
 
   void set stencil(bool value) native "this.stencil = value;";
 }