Change the toString method of IterableBase/IterableMixin to show some elements.

sdk/lib/collection/queue.dart

Index: sdk/lib/collection/queue.dart
diff --git a/sdk/lib/collection/queue.dart b/sdk/lib/collection/queue.dart
index 1cacd18c18fc158784ff2fd0692a4b06e3e8a80d..86035c5000f28950aebd3ee43c3f8e859858887e 100644
--- a/sdk/lib/collection/queue.dart
+++ b/sdk/lib/collection/queue.dart
@@ -297,9 +297,6 @@ class DoubleLinkedQueue<E> extends IterableBase<E> implements Queue<E> {
   _DoubleLinkedQueueIterator<E> get iterator {
     return new _DoubleLinkedQueueIterator<E>(_sentinel);
   }
-
-  // TODO(zarah)  Remove this, and let it be inherited by IterableBase
-  String toString() => IterableMixinWorkaround.toStringIterable(this, '{', '}');
 }
 
 class _DoubleLinkedQueueIterator<E> implements Iterator<E> {
@@ -526,9 +523,6 @@ class ListQueue<E> extends IterableBase<E> implements Queue<E> {
     }
   }
 
-  // TODO(zarah)  Remove this, and let it be inherited by IterableBase
-  String toString() => IterableMixinWorkaround.toStringIterable(this, '{', '}');
-
   // Queue interface.
 
   void addLast(E element) { _add(element); }