fixes #52, fields shadowing getters/setters or other fields

lib/runtime/dart/collection.js

 var collection;
 (function(exports) {
   'use strict';
   let _source = Symbol('_source');
   let UnmodifiableListView$ = dart.generic(function(E) {
     class UnmodifiableListView extends _internal.UnmodifiableListBase$(E) {
       UnmodifiableListView(source) {
         this[_source] = source;
         super.UnmodifiableListBase();
       }
@@ skipping 949 matching lines @@
     }
     IterableBase[dart.implements] = () => [core.Iterable$(E)];
     dart.defineLazyProperties(IterableBase, {
       get _toStringVisiting() {
         return new core.List.from([]);
       }
     });
     return IterableBase;
   });
   let IterableBase = IterableBase$();
+  let _NOT_MOVED_YET = Symbol('_NOT_MOVED_YET');
   let _iterator = Symbol('_iterator');
-  let _NOT_MOVED_YET = Symbol('_NOT_MOVED_YET');
   let _state = Symbol('_state');
   let _move = Symbol('_move');
   let _HAS_NEXT_AND_NEXT_IN_CURRENT = Symbol('_HAS_NEXT_AND_NEXT_IN_CURRENT');
   let _NO_NEXT = Symbol('_NO_NEXT');
   let HasNextIterator$ = dart.generic(function(E) {
     class HasNextIterator extends core.Object {
       HasNextIterator(iterator) {
         this[_iterator] = iterator;
         this[_state] = HasNextIterator[_NOT_MOVED_YET];
       }
@@ skipping 3977 matching lines @@
   exports.LinkedHashMapKeyIterable$ = LinkedHashMapKeyIterable$;
   exports.LinkedHashMapKeyIterable = LinkedHashMapKeyIterable;
   exports.LinkedHashMapKeyIterator$ = LinkedHashMapKeyIterator$;
   exports.LinkedHashMapKeyIterator = LinkedHashMapKeyIterator;
   exports.HashSetIterator$ = HashSetIterator$;
   exports.HashSetIterator = HashSetIterator;
   exports.LinkedHashSetCell = LinkedHashSetCell;
   exports.LinkedHashSetIterator$ = LinkedHashSetIterator$;
   exports.LinkedHashSetIterator = LinkedHashSetIterator;
 })(collection || (collection = {}));