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

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

Index: client/dom/generated/src/frog/SVGElement.dart
diff --git a/client/dom/generated/src/frog/SVGElement.dart b/client/dom/generated/src/frog/SVGElement.dart
index 26ae2c0f3cc485864e58a5a8f9373f4cd83d0d3e..9c0d98dab5af9ba96e403570651c5ec29b8aca07 100644
--- a/client/dom/generated/src/frog/SVGElement.dart
+++ b/client/dom/generated/src/frog/SVGElement.dart
@@ -1,13 +1,13 @@
 
-class SVGElementJs extends ElementJs implements SVGElement native "*SVGElement" {
+class _SVGElementJs extends _ElementJs implements SVGElement native "*SVGElement" {
 
   String get id() native "return this.id;";
 
   void set id(String value) native "this.id = value;";
 
-  SVGSVGElementJs get ownerSVGElement() native "return this.ownerSVGElement;";
+  _SVGSVGElementJs get ownerSVGElement() native "return this.ownerSVGElement;";
 
-  SVGElementJs get viewportElement() native "return this.viewportElement;";
+  _SVGElementJs get viewportElement() native "return this.viewportElement;";
 
   String get xmlbase() native "return this.xmlbase;";