Add a comment for the #if-0 block in scoped_nsobject_unittest.mm.

base/mac/scoped_nsobject_unittest.mm

Index: base/mac/scoped_nsobject_unittest.mm
diff --git a/base/mac/scoped_nsobject_unittest.mm b/base/mac/scoped_nsobject_unittest.mm
index c838217a9eec1e720bc10da5c5394df0f1b60adf..8b0b97df3a72df06e987cd09032bd23cbd2a05f2 100644
--- a/base/mac/scoped_nsobject_unittest.mm
+++ b/base/mac/scoped_nsobject_unittest.mm
@@ -52,6 +52,8 @@ TEST(ScopedNSObjectTest, ScopedNSObject) {
   ASSERT_EQ(2u, [p1 retainCount]);
 }
 
+// Instantiating scoped_nsobject<> with T=NSAutoreleasePool should trip a
+// static_assert.
 #if 0
 TEST(ScopedNSObjectTest, FailToCreateScopedNSObjectAutoreleasePool) {
   base::scoped_nsobject<NSAutoreleasePool> pool;