Add a comment about why we don't implement dir_reader_posix.h on OS X.
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@41313 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/base/dir_reader_posix.h b/base/dir_reader_posix.h
index e9ad11e4..7f069b63 100644
--- a/base/dir_reader_posix.h
+++ b/base/dir_reader_posix.h
@@ -11,6 +11,12 @@
// read from directories without allocating memory. For the interface, see
// the generic fallback in dir_reader_fallback.h.
+// Mac note: OS X has getdirentries, but it only works if we restrict Chrome to
+// 32-bit inodes. There is a getdirentries64 syscall in 10.6, but it's not
+// wrapped and the direct syscall interface is unstable. Using an unstable API
+// seems worse than falling back to enumerating all file descriptors so we will
+// probably never implement this on the Mac.
+
#if defined(OS_LINUX)
#include "base/dir_reader_linux.h"
#else
