Revert "Move toString() to collection classes."

sdk/lib/collection/linked_list.dart

Index: sdk/lib/collection/linked_list.dart
diff --git a/sdk/lib/collection/linked_list.dart b/sdk/lib/collection/linked_list.dart
index 502341ce1f1a3ae919fb02e4232e0e3f883f4afd..a9c898969429e27cbe854b7cf577c6acfb06c7bc 100644
--- a/sdk/lib/collection/linked_list.dart
+++ b/sdk/lib/collection/linked_list.dart
@@ -14,7 +14,6 @@ part of dart.collection;
 class LinkedList<E extends LinkedListEntry<E>>
     extends IterableBase<E>
     implements _LinkedListLink {
-
   int _modificationCount = 0;
   int _length = 0;
   _LinkedListLink _next;
@@ -61,8 +60,7 @@ class LinkedList<E extends LinkedListEntry<E>>
 
   Iterator<E> get iterator => new _LinkedListIterator<E>(this);
 
-  // TODO(zarah) Remove this, and let it be inherited by IterableMixin
-  String toString() => IterableMixinWorkaround.toStringIterable(this, '{', '}');
+  String toString() => ToString.iterableToString(this);
 
   int get length => _length;