Revert "Add "last" setter to List."

pkg/collection/lib/wrappers.dart

Index: pkg/collection/lib/wrappers.dart
diff --git a/pkg/collection/lib/wrappers.dart b/pkg/collection/lib/wrappers.dart
index 7723d58f74dea5be390034a46c0025e8d37187d7..2034174259151097f59ab8bb6bd23e27661be4ff 100644
--- a/pkg/collection/lib/wrappers.dart
+++ b/pkg/collection/lib/wrappers.dart
@@ -124,10 +124,6 @@ class DelegatingList<E> extends DelegatingIterable<E> implements List<E> {
     _listBase[index] = value;
   }
 
-  void set last(E value) {
-    _listBase.last = value;
-  }
-
   void add(E value) {
     _listBase.add(value);
   }
@@ -431,7 +427,7 @@ class MapKeySet<E> extends _DelegatingIterableBase<E>
 
 /**
  * Creates a modifiable [Set] view of the values of a [Map].
- *
+ * 
  * The `Set` view assumes that the keys of the `Map` can be uniquely determined
  * from the values. The `keyForValue` function passed to the constructor finds
  * the key for a single value. The `keyForValue` function should be consistent