A quick fix for Mac GCC.

net/base/crl_set.cc

Index: net/base/crl_set.cc
===================================================================
--- net/base/crl_set.cc	(revision 108043)
+++ net/base/crl_set.cc	(working copy)
@@ -410,7 +410,7 @@
     const base::StringPiece& parent_spki) const {
   base::StringPiece serial(serial_number);
 
-  if (!serial.empty() && serial[0] >= 0x80) {
+  if (!serial.empty() && static_cast<unsigned char>(serial[0]) >= 0x80) {

[wtc, 2011/11/01 04:02:51]

It may be better to use bit testing:
  (serial[0] & 0x80) != 0

[Hironori Bono, 2011/11/01 07:57:52]

Done. Thanks for your suggestion. It also fixes the bot.

     // This serial number is negative but the process which generates CRL sets
     // will reject any certificates with negative serial numbers as invalid.
     return UNKNOWN;