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

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

Index: client/dom/generated/src/frog/CSSPrimitiveValue.dart
diff --git a/client/dom/generated/src/frog/CSSPrimitiveValue.dart b/client/dom/generated/src/frog/CSSPrimitiveValue.dart
index 975a6d756e838409c7bd38a514e614eae3695b20..fbfade3ca3cc4a3768ef5c77c336d1a5eaa4c725 100644
--- a/client/dom/generated/src/frog/CSSPrimitiveValue.dart
+++ b/client/dom/generated/src/frog/CSSPrimitiveValue.dart
@@ -1,5 +1,5 @@
 
-class CSSPrimitiveValueJs extends CSSValueJs implements CSSPrimitiveValue native "*CSSPrimitiveValue" {
+class _CSSPrimitiveValueJs extends _CSSValueJs implements CSSPrimitiveValue native "*CSSPrimitiveValue" {
 
   static final int CSS_ATTR = 22;
 
@@ -55,13 +55,13 @@ class CSSPrimitiveValueJs extends CSSValueJs implements CSSPrimitiveValue native
 
   int get primitiveType() native "return this.primitiveType;";
 
-  CounterJs getCounterValue() native;
+  _CounterJs getCounterValue() native;
 
   num getFloatValue(int unitType) native;
 
-  RGBColorJs getRGBColorValue() native;
+  _RGBColorJs getRGBColorValue() native;
 
-  RectJs getRectValue() native;
+  _RectJs getRectValue() native;
 
   String getStringValue() native;