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

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

Index: client/dom/generated/src/frog/FileWriter.dart
diff --git a/client/dom/generated/src/frog/FileWriter.dart b/client/dom/generated/src/frog/FileWriter.dart
index 67422280bb8eb1f4032300e6181fd5bd97208101..f1af0d308ed78a1bce9659d7acd9b836f7c0e4d0 100644
--- a/client/dom/generated/src/frog/FileWriter.dart
+++ b/client/dom/generated/src/frog/FileWriter.dart
@@ -1,5 +1,5 @@
 
-class FileWriterJs extends DOMTypeJs implements FileWriter native "*FileWriter" {
+class _FileWriterJs extends _DOMTypeJs implements FileWriter native "*FileWriter" {
 
   static final int DONE = 2;
 
@@ -7,7 +7,7 @@ class FileWriterJs extends DOMTypeJs implements FileWriter native "*FileWriter"
 
   static final int WRITING = 1;
 
-  FileErrorJs get error() native "return this.error;";
+  _FileErrorJs get error() native "return this.error;";
 
   int get length() native "return this.length;";
 
@@ -45,5 +45,5 @@ class FileWriterJs extends DOMTypeJs implements FileWriter native "*FileWriter"
 
   void truncate(int size) native;
 
-  void write(BlobJs data) native;
+  void write(_BlobJs data) native;
 }