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

base/mac/scoped_nsobject_unittest.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <vector>
 
 #include "base/mac/scoped_nsautorelease_pool.h"
 #include "base/mac/scoped_nsobject.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 34 matching lines @@
   ASSERT_EQ(3u, [p6 retainCount]);
   {
     base::mac::ScopedNSAutoreleasePool pool;
     p6.autorelease();
     ASSERT_EQ(nil, p6.get());
     ASSERT_EQ(3u, [p1 retainCount]);
   }
   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;
 }
 #endif
 
 TEST(ScopedNSObjectTest, ScopedNSObjectInContainer) {
   base::scoped_nsobject<id> p([[NSObject alloc] init]);
   ASSERT_TRUE(p.get());
   ASSERT_EQ(1u, [p retainCount]);
@@ skipping 17 matching lines @@
   base::scoped_nsobject<id> p2([[NSObject alloc] init]);
   ASSERT_TRUE(o1 != p2);
   ASSERT_FALSE(o1 == p2);
   id o2 = p2.get();
   swap(p1, p2);
   ASSERT_EQ(o2, p1.get());
   ASSERT_EQ(o1, p2.get());
 }
 
 }  // namespace