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

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

 
 class _RangeJs extends _DOMTypeJs implements Range native "*Range" {
 
   static final int END_TO_END = 2;
 
   static final int END_TO_START = 3;
 
   static final int NODE_AFTER = 1;
 
   static final int NODE_BEFORE = 0;
 
   static final int NODE_BEFORE_AND_AFTER = 2;
 
   static final int NODE_INSIDE = 3;
 
   static final int START_TO_END = 1;
 
   static final int START_TO_START = 0;
 
-  bool get collapsed() native "return this.collapsed;";
+  final bool collapsed;
 
-  _NodeJs get commonAncestorContainer() native "return this.commonAncestorContainer;";
+  final _NodeJs commonAncestorContainer;
 
-  _NodeJs get endContainer() native "return this.endContainer;";
+  final _NodeJs endContainer;
 
-  int get endOffset() native "return this.endOffset;";
+  final int endOffset;
 
-  _NodeJs get startContainer() native "return this.startContainer;";
+  final _NodeJs startContainer;
 
-  int get startOffset() native "return this.startOffset;";
+  final int startOffset;
 
   _DocumentFragmentJs cloneContents() native;
 
   _RangeJs cloneRange() native;
 
   void collapse(bool toStart) native;
 
   int compareNode(_NodeJs refNode) native;
 
   int comparePoint(_NodeJs refNode, int offset) native;
@@ skipping 31 matching lines @@
   void setStart(_NodeJs refNode, int offset) native;
 
   void setStartAfter(_NodeJs refNode) native;
 
   void setStartBefore(_NodeJs refNode) native;
 
   void surroundContents(_NodeJs newParent) native;
 
   String toString() native;
 }