PBKDF2 implemetation using NSS.

BUG=none
TEST=unit test

Review URL: http://codereview.chromium.org/1024001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@42247 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/base/nss_util.h b/base/nss_util.h
index f7662289..5c8e0f6 100644
--- a/base/nss_util.h
+++ b/base/nss_util.h
@@ -7,6 +7,9 @@
 
 #include "base/basictypes.h"
 
+// This file specifically doesn't depend on any NSS or NSPR headers because it
+// is included by various (non-crypto) parts of chrome to call the
+// initialization functions.
 namespace base {
 
 class Time;