Revert "Add "last" setter to List."

pkg/third_party/html5lib/lib/src/list_proxy.dart

Index: pkg/third_party/html5lib/lib/src/list_proxy.dart
diff --git a/pkg/third_party/html5lib/lib/src/list_proxy.dart b/pkg/third_party/html5lib/lib/src/list_proxy.dart
index 866d0ec72cf2770d8ae605ae0a618a7982ba5abb..0ba70733b4474e603b237cd63d75e996b7c10481 100644
--- a/pkg/third_party/html5lib/lib/src/list_proxy.dart
+++ b/pkg/third_party/html5lib/lib/src/list_proxy.dart
@@ -47,7 +47,6 @@ class ListProxy<E> extends IterableBase<E> implements List<E> {
   set length(int value) { _list.length = value; }
   void add(E value) { _list.add(value); }
 
-  void set last(E value) { _list.last = value; }
   void addLast(E value) { add(value); }
   void addAll(Iterable<E> collection) { _list.addAll(collection); }
   void sort([int compare(E a, E b)]) { _list.sort(compare); }