Add optional context for certificate errors.

net/cert/internal/cert_error_id.cc

Index: net/cert/internal/cert_error_id.cc
diff --git a/net/cert/internal/cert_error_id.cc b/net/cert/internal/cert_error_id.cc
new file mode 100644
index 0000000000000000000000000000000000000000..80ab4f4f214dcbbcdbe707233fc3b244dc8eadc1
--- /dev/null
+++ b/net/cert/internal/cert_error_id.cc
@@ -0,0 +1,14 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/cert/internal/cert_error_id.h"
+
+namespace net {
+
+const char* CertErrorIdToDebugString(CertErrorId id) {
+  // The CertErrorId is simply a pointer for a C-string literal.
+  return reinterpret_cast<const char*>(id);
+}
+
+}  // namespace net