Trace lists when they are stored into other lists.

tests/compiler/dart2js/list_tracer_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:expect/expect.dart';
 import "package:async_helper/async_helper.dart";
 import
     '../../../sdk/lib/_internal/compiler/implementation/types/types.dart'
     show ContainerTypeMask, TypeMask;
 
@@ skipping 69 matching lines @@
 var listUnset = $listAllocation;
 var listOnlySetWithConstraint = $listAllocation;
 var listEscapingInSetterValue = $listAllocation;
 var listEscapingInIndex = $listAllocation;
 var listEscapingInIndexSet = $listAllocation;
 var listEscapingTwiceInIndexSet = $listAllocation;
 var listPassedAsOptionalParameter = $listAllocation;
 var listPassedAsNamedParameter = $listAllocation;
 var listSetInNonFinalField = $listAllocation;
 var listWithChangedLength = $listAllocation;
+var listStoredInList = $listAllocation;
+var listStoredInListButEscapes = $listAllocation;
 
 foo(list) {
   list[0] = aDouble;
 }
 
 bar() {
   return listReturnedFromMethod;
 }
 
 takeOptional([list]) {
@@ skipping 68 matching lines @@
   takeOptional(listPassedAsOptionalParameter);
 
   listPassedAsNamedParameter[0] = anInt;
   takeNamed(list: listPassedAsNamedParameter);
 
   listSetInNonFinalField[0] = anInt;
   new B(listSetInNonFinalField);
 
   listWithChangedLength[0] = anInt;
   listWithChangedLength.length = 54;
+
+  a = [listStoredInList];
+  a[0][0] = 42;
+
+  a = [listStoredInListButEscapes];
+  a[0][0] = 42;
+  a.forEach((e) => print(e));
 }
 """;
 }
 
 void main() {
   doTest('[]', nullify: false); // Test literal list.
   doTest('new List()', nullify: false); // Test growable list.
   doTest('new List(1)', nullify: true); // Test fixed list.
   doTest('new List.filled(1, 0)', nullify: false); // Test List.filled.
   doTest('new List.filled(1, null)', nullify: true); // Test List.filled.
@@ skipping 29 matching lines @@
     checkType('listEscapingInIndexSet', typesTask.uint31Type);
     checkType('listEscapingTwiceInIndexSet', typesTask.numType);
     checkType('listSetInNonFinalField', typesTask.numType);
     checkType('listWithChangedLength', typesTask.uint31Type.nullable());
 
     checkType('listPassedToClosure', typesTask.dynamicType);
     checkType('listReturnedFromClosure', typesTask.dynamicType);
     checkType('listUsedWithNonOkSelector', typesTask.dynamicType);
     checkType('listPassedAsOptionalParameter', typesTask.numType);
     checkType('listPassedAsNamedParameter', typesTask.numType);
+    checkType('listStoredInList', typesTask.uint31Type);
+    checkType('listStoredInListButEscapes', typesTask.dynamicType);
 
     if (!allocation.contains('filled')) {
       checkType('listUnset', new TypeMask.nonNullEmpty());
       checkType('listOnlySetWithConstraint', new TypeMask.nonNullEmpty());
     }
   }));
 }