Change List constructors.

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 7a6c06a904eb5d64b999424895bf2ed77e8535a4..25ab6393fb92b0eec1824a38dd3b15f22756adbe 100644
--- a/sdk/lib/html/dart2js/html_dart2js.dart
+++ b/sdk/lib/html/dart2js/html_dart2js.dart
@@ -24950,7 +24950,7 @@ class _Copier extends _MessageTraverser {
     int len = list.length;
 
     // TODO(floitsch): we loose the generic type of the List.
-    copy = new List(len);
+    copy = new List.fixedLength(len);
     _visited[list] = copy;
     for (int i = 0; i < len; i++) {
       copy[i] = _dispatch(list[i]);
@@ -25004,7 +25004,7 @@ class _Serializer extends _MessageTraverser {
 
   _serializeList(List list) {
     int len = list.length;
-    var result = new List(len);
+    var result = new List.fixedLength(len);
     for (int i = 0; i < len; i++) {
       result[i] = _dispatch(list[i]);
     }