Use fields in hidden native DOM classes instead of getters/setters.

client/dom/generated/src/frog/Uint8Array.dart

 
 class _Uint8ArrayJs extends _ArrayBufferViewJs implements Uint8Array, List<int> native "*Uint8Array" {
 
   factory Uint8Array(int length) =>  _construct_Uint8Array(length);
 
   factory Uint8Array.fromList(List<int> list) => _construct_Uint8Array(list);
 
   factory Uint8Array.fromBuffer(ArrayBuffer buffer) => _construct_Uint8Array(buffer);
 
   static _construct_Uint8Array(arg) native 'return new Uint8Array(arg);';
 
   static final int BYTES_PER_ELEMENT = 1;
 
-  int get length() native "return this.length;";
+  final int length;
 
   int operator[](int index) native "return this[index];";
 
   void operator[]=(int index, int value) native "this[index] = value";
   // -- start List<int> mixins.
   // int is the element type.
 
   // From Iterable<int>:
 
   Iterator<int> iterator() {
@@ skipping 56 matching lines @@
   }
   List<int> getRange(int start, int length) =>
       _Lists.getRange(this, start, length, <int>[]);
 
   // -- end List<int> mixins.
 
   void setElements(Object array, [int offset = null]) native;
 
   _Uint8ArrayJs subarray(int start, [int end = null]) native;
 }