Call reset(nullptr) in scoped_ptr's.

base/memory/scoped_ptr_unittest.cc

Index: base/memory/scoped_ptr_unittest.cc
diff --git a/base/memory/scoped_ptr_unittest.cc b/base/memory/scoped_ptr_unittest.cc
index 71d995c452e826ad1faeb28f315433077f338e88..eb5bf000c48596d12ae97c59aad7c7eaf734ea06 100644
--- a/base/memory/scoped_ptr_unittest.cc
+++ b/base/memory/scoped_ptr_unittest.cc
@@ -709,10 +709,20 @@ TEST(ScopedPtrTest, ReferenceCycle) {
   a->b.reset(new StructB);
   a->b->a.reset(a);
 
-  // Break the cycle by calling reset(). This will cause |a| (and hence, |a.b|)
+  // Break the cycle by calling reset(). This will cause |a| (and hence, |a->b|)
   // to be deleted before the call to reset() returns. This tests that the
   // implementation of scoped_ptr::reset() doesn't access |this| after it
   // deletes the underlying pointer. This behaviour is consistent with the
   // definition of unique_ptr::reset in C++11.
   a->b.reset();
+
+  // Go again, but this time, break the cycle by invoking |a|'s destructor. This
+  // tests that the implementation of ~scoped_ptr doesn't infinitely recurse
+  // into the destructors of |a| and |a->b|. Note, deleting |a| instead will
+  // cause |a| to be double-free'd because |a->b| owns |a| and deletes it via
+  // its destructor.
+  a = new StructA;
+  a->b.reset(new StructB);
+  a->b->a.reset(a);
+  a->~StructA();
 }