Remember if a user declines to provide a server with a client certificate

net/base/ssl_client_auth_cache.cc

Index: net/base/ssl_client_auth_cache.cc
diff --git a/net/base/ssl_client_auth_cache.cc b/net/base/ssl_client_auth_cache.cc
index d2f47cc2b0c61a92335fa7e59657b05ec8253875..d16d4df1e19d479cc1ae07c8e85bcbac2e6670d7 100644
--- a/net/base/ssl_client_auth_cache.cc
+++ b/net/base/ssl_client_auth_cache.cc
@@ -4,15 +4,26 @@
 
 #include "net/base/ssl_client_auth_cache.h"
 
+#include "base/logging.h"
+#include "net/base/x509_certificate.h"
+
 namespace net {
 
 SSLClientAuthCache::SSLClientAuthCache() {}
 
 SSLClientAuthCache::~SSLClientAuthCache() {}
 
-X509Certificate* SSLClientAuthCache::Lookup(const std::string& server) {
+bool SSLClientAuthCache::Lookup(const std::string& server,
+                                X509Certificate** certificate) {
+  DCHECK(certificate);
+  *certificate = NULL;
+
   AuthCacheMap::iterator iter = cache_.find(server);
-  return (iter == cache_.end()) ? NULL : iter->second;
+  if (iter == cache_.end())
+    return false;
+
+  *certificate = iter->second;
+  return true;
 }
 
 void SSLClientAuthCache::Add(const std::string& server,