Make List.remove return boolean.

tests/corelib/queue_test.dart

 // Copyright (c) 2011, 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.
 
 library queue.test;
 
 import "package:expect/expect.dart";
 import 'dart:collection';
 
 abstract class QueueTest {
@@ skipping 204 matching lines @@
     for (int i = 1; i <= 5; i++) {
       Expect.equals(i, queue.removeFirst());
       testLength(40 - i, queue);
     }
 
     for (int i = 1; i <= 5; i++) {
       Expect.equals(11 - i, queue.removeLast());
       testLength(35 - i, queue);
     }
 
-    queue.remove(10);
+    Expect.isTrue(queue.remove(10));
+    testLength(29, queue);
+    Expect.isFalse(queue.remove(999));
     testLength(29, queue);
 
     queue.removeWhere((x) => x == 7);
     testLength(26, queue);
 
     queue.retainWhere((x) => x != 3);
     testLength(23, queue);
 
     Expect.listEquals(
         [6, 8, 9, 1, 2, 4, 5, 6, 8, 9, 10, 1, 2, 4, 5, 6, 8, 9, 10, 1, 2, 4, 5],
@@ skipping 24 matching lines @@
       Expect.equals(-i, mapped.first);
       Expect.equals(i + 1, skip1.first);
       Expect.equals(i, queue.removeFirst());
       Expect.equals(i + 1, take1.first);
       Expect.equals(-i - 1, mapped.first);
       Expect.equals(N - 1 - i, queue.last);
       Expect.equals(N - 1 - i, queue.removeLast());
     }
     Expect.equals(N - 1000, queue.length);
 
-    queue.remove(N >> 1);
+    Expect.isTrue(queue.remove(N >> 1));
     Expect.equals(N - 1001, queue.length);
 
     queue.clear();
     Expect.equals(0, queue.length);
     Expect.isTrue(queue.isEmpty);
 
     queue.addAll(set);
     Expect.equals(N, queue.length);
     Expect.isFalse(queue.isEmpty);
 
@@ skipping 117 matching lines @@
     }
     Expect.equals(null, entry2);
   }
 }
 
 
 main() {
   new DoubleLinkedQueueTest().testMain();
   new ListQueueTest().testMain();
 }