Roll NSS to r137999

Speculative fix for mac_shared

BUG=none
TEST=mac_shared goes green
R=thakis


Review URL: https://chromiumcodereview.appspot.com/10387204

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@138027 0039d316-1c4b-4281-b951-d872f2087c98

DEPS

@@ -59,7 +59,7 @@ vars = {
   "v8_revision": "11594",
   "webrtc_revision": "2180",
   "jsoncpp_revision": "248",
-  "nss_revision": "137925",
+  "nss_revision": "137999",
   "rlz_revision": "128",
 }