Add "last" setter to List.

sdk/lib/html/dart2js/html_dart2js.dart

Index: sdk/lib/html/dart2js/html_dart2js.dart
diff --git a/sdk/lib/html/dart2js/html_dart2js.dart b/sdk/lib/html/dart2js/html_dart2js.dart
index 050e4c08aa9517e27436f05480a079e4c67b679a..b5eb75a59329b3c2b5a7cd909f0e6adcd5e51ce0 100644
--- a/sdk/lib/html/dart2js/html_dart2js.dart
+++ b/sdk/lib/html/dart2js/html_dart2js.dart
@@ -33250,7 +33250,11 @@ abstract class ImmutableListMixin<E> implements List<E> {
     return new FixedSizeListIterator<E>(this);
   }
 
-  // From Collection<E>:
+  // From List<E>:
+  void set last(E value) {
+    throw new UnsupportedError("Cannot modify an immutable List.");
+  }
+
   void add(E value) {
     throw new UnsupportedError("Cannot add to immutable List.");
   }
@@ -33259,7 +33263,6 @@ abstract class ImmutableListMixin<E> implements List<E> {
     throw new UnsupportedError("Cannot add to immutable List.");
   }
 
-  // From List<E>:
   void sort([int compare(E a, E b)]) {
     throw new UnsupportedError("Cannot sort immutable List.");
   }