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

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

 
-class HTMLMeterElementJs extends HTMLElementJs implements HTMLMeterElement native "*HTMLMeterElement" {
+class _HTMLMeterElementJs extends _HTMLElementJs implements HTMLMeterElement native "*HTMLMeterElement" {
 
-  HTMLFormElementJs get form() native "return this.form;";
+  _HTMLFormElementJs get form() native "return this.form;";
 
   num get high() native "return this.high;";
 
   void set high(num value) native "this.high = value;";
 
-  NodeListJs get labels() native "return this.labels;";
+  _NodeListJs get labels() native "return this.labels;";
 
   num get low() native "return this.low;";
 
   void set low(num value) native "this.low = value;";
 
   num get max() native "return this.max;";
 
   void set max(num value) native "this.max = value;";
 
   num get min() native "return this.min;";
 
   void set min(num value) native "this.min = value;";
 
   num get optimum() native "return this.optimum;";
 
   void set optimum(num value) native "this.optimum = value;";
 
   num get value() native "return this.value;";
 
   void set value(num value) native "this.value = value;";
 }