Don't allow negative date components in ParseCertificateDate(), or ones starting with a plus.

net/cert/x509_cert_types.cc

Index: net/cert/x509_cert_types.cc
diff --git a/net/cert/x509_cert_types.cc b/net/cert/x509_cert_types.cc
index bfb875cf56c138868996097013b1451c59713598..766a1f0429b3a6add189dc7ba5065d5e5cd982b8 100644
--- a/net/cert/x509_cert_types.cc
+++ b/net/cert/x509_cert_types.cc
@@ -8,9 +8,9 @@
 #include <cstring>
 
 #include "base/logging.h"
-#include "base/strings/string_number_conversions.h"
 #include "base/strings/string_piece.h"
 #include "base/time/time.h"
+#include "net/base/parse_number.h"
 #include "net/cert/x509_certificate.h"
 
 namespace net {
@@ -23,7 +23,8 @@ namespace {
 // untouched otherwise. Returns the parsed integer.
 int ParseIntAndAdvance(const char** field, size_t field_len, bool* ok) {
   int result = 0;
-  *ok &= base::StringToInt(base::StringPiece(*field, field_len), &result);
+  *ok &=
+      ParseNonNegativeDecimalInt(base::StringPiece(*field, field_len), &result);
   *field += field_len;
   return result;
 }