Revert r73401 per Raymond Hettinger's request.

The rational is the change might cause imcompatiblity problems with
PyYAML. In addition, Raymond wants to kept the different versions of
collections synchronized across Python versions.

Lib/collections.py

@@ -99,16 +99,14 @@ class OrderedDict(dict, MutableMapping):
 
     def __reduce__(self):
         'Return state information for pickling'
-        dictitems = self.iteritems()
+        items = [[k, self[k]] for k in self]
         tmp = self.__map, self.__root
         del self.__map, self.__root
         inst_dict = vars(self).copy()
         self.__map, self.__root = tmp
-        # Set the state item to None when the dictionary is empty. This saves
-        # about 2 opcodes when the object is pickled.
-        if not inst_dict:
-            inst_dict = None
-        return (self.__class__, (), inst_dict, None, dictitems)
+        if inst_dict:
+            return (self.__class__, (items,), inst_dict)
+        return self.__class__, (items,)
 
     setdefault = MutableMapping.setdefault
     update = MutableMapping.update

Lib/test/test_collections.py

@@ -795,9 +795,9 @@ class TestOrderedDict(unittest.TestCase):
         # do not save instance dictionary if not needed
         pairs = [('c', 1), ('b', 2), ('a', 3), ('d', 4), ('e', 5), ('f', 6)]
         od = OrderedDict(pairs)
+        self.assertEqual(len(od.__reduce__()), 2)
         od.x = 10
-        self.assertGreaterEqual(len(od.__reduce__()), 2)
-        self.assertLessEqual(len(od.__reduce__()), 5)
+        self.assertEqual(len(od.__reduce__()), 3)
 
     def test_repr(self):
         od = OrderedDict([('c', 1), ('b', 2), ('a', 3), ('d', 4), ('e', 5), ('f', 6)])