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

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

 
-class SVGDescElementJs extends SVGElementJs implements SVGDescElement native "*SVGDescElement" {
+class _SVGDescElementJs extends _SVGElementJs implements SVGDescElement native "*SVGDescElement" {
 
   // From SVGLangSpace
 
   String get xmllang() native "return this.xmllang;";
 
   void set xmllang(String value) native "this.xmllang = value;";
 
   String get xmlspace() native "return this.xmlspace;";
 
   void set xmlspace(String value) native "this.xmlspace = value;";
 
   // From SVGStylable
 
-  SVGAnimatedStringJs get className() native "return this.className;";
+  _SVGAnimatedStringJs get className() native "return this.className;";
 
-  CSSStyleDeclarationJs get style() native "return this.style;";
+  _CSSStyleDeclarationJs get style() native "return this.style;";
 
-  CSSValueJs getPresentationAttribute(String name) native;
+  _CSSValueJs getPresentationAttribute(String name) native;
 }