Remove uses of IterableMixinWorkaround outside of VM and dart2js lists.

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 5dfe17089c21fe8f62c75fa3dfa7ad44b9669490..b648bc58833426101b0cad1472721b4a340a9aba 100644
--- a/sdk/lib/collection/queue.dart
+++ b/sdk/lib/collection/queue.dart
@@ -317,8 +317,7 @@ class DoubleLinkedQueue<E> extends IterableBase<E> implements Queue<E> {
     return new _DoubleLinkedQueueIterator<E>(_sentinel);
   }
 
-  // TODO(zarah)  Remove this, and let it be inherited by IterableBase
-  String toString() => IterableMixinWorkaround.toStringIterable(this, '{', '}');
+  String toString() => _collectionToString(this, '{', '}');
 }
 
 class _DoubleLinkedQueueIterator<E> implements Iterator<E> {
@@ -537,8 +536,7 @@ 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, '{', '}');
+  String toString() => _collectionToString(this, '{', '}');
 
   // Queue interface.