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

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

Index: client/dom/generated/src/frog/Clipboard.dart
diff --git a/client/dom/generated/src/frog/Clipboard.dart b/client/dom/generated/src/frog/Clipboard.dart
index 4fff899fdf287156d77129f2e9bb19b6b0be32de..8a934bc0c1b00e1a3c7571b5368dc75fc92d026c 100644
--- a/client/dom/generated/src/frog/Clipboard.dart
+++ b/client/dom/generated/src/frog/Clipboard.dart
@@ -1,5 +1,5 @@
 
-class ClipboardJs extends DOMTypeJs implements Clipboard native "*Clipboard" {
+class _ClipboardJs extends _DOMTypeJs implements Clipboard native "*Clipboard" {
 
   String get dropEffect() native "return this.dropEffect;";
 
@@ -9,9 +9,9 @@ class ClipboardJs extends DOMTypeJs implements Clipboard native "*Clipboard" {
 
   void set effectAllowed(String value) native "this.effectAllowed = value;";
 
-  FileListJs get files() native "return this.files;";
+  _FileListJs get files() native "return this.files;";
 
-  DataTransferItemListJs get items() native "return this.items;";
+  _DataTransferItemListJs get items() native "return this.items;";
 
   List get types() native "return this.types;";
 
@@ -21,5 +21,5 @@ class ClipboardJs extends DOMTypeJs implements Clipboard native "*Clipboard" {
 
   bool setData(String type, String data) native;
 
-  void setDragImage(HTMLImageElementJs image, int x, int y) native;
+  void setDragImage(_HTMLImageElementJs image, int x, int y) native;
 }