Check that we've got a complete header before accessing its fields.

base/pickle.h

Index: base/pickle.h
===================================================================
--- base/pickle.h	(revision 72619)
+++ base/pickle.h	(working copy)
@@ -236,6 +236,7 @@
 
   FRIEND_TEST_ALL_PREFIXES(PickleTest, Resize);
   FRIEND_TEST_ALL_PREFIXES(PickleTest, FindNext);
+  FRIEND_TEST_ALL_PREFIXES(PickleTest, FindNextWithIncompleteHeader);
   FRIEND_TEST_ALL_PREFIXES(PickleTest, IteratorHasRoom);
 };