Move toString() to collection classes.

runtime/lib/array.dart

Index: runtime/lib/array.dart
diff --git a/runtime/lib/array.dart b/runtime/lib/array.dart
index e7f88a3ddb70525e20e355a8f54c50925bee8165..e16cbef904c657979f7124d82b9b251a687e3adb 100644
--- a/runtime/lib/array.dart
+++ b/runtime/lib/array.dart
@@ -14,7 +14,7 @@ class _ObjectArray<E> implements List<E> {
   void operator []=(int index, E value) native "ObjectArray_setIndexed";
 
   String toString() {
-    return ToString.iterableToString(this);
+    return IterableMixinWorkaround.toStringIterable(this,'[' , ']');
   }
 
   int get length native "ObjectArray_getLength";
@@ -457,7 +457,7 @@ class _ImmutableArray<E> implements List<E> {
   }
 
   String toString() {
-    return ToString.iterableToString(this);
+    return IterableMixinWorkaround.toStringIterable(this, '[', ']');
   }
 
   int indexOf(Object element, [int start = 0]) {