Add const to a pair of x509 certificate methods.

Doesn't actually modify the method bodies at all.

Change-Id: I7354db324deeee4bfeb497038a704d9cbb98d961
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1733789Reviewed-by: David Benjamin <davidben@chromium.org>
Commit-Queue: Matt Menke <mmenke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683765}

net/cert/x509_certificate.cc

@@ -327,7 +327,7 @@ CertificateList X509Certificate::CreateCertificateListFromBytes(
   return results;
 }
 
-void X509Certificate::Persist(base::Pickle* pickle) {
+void X509Certificate::Persist(base::Pickle* pickle) const {
   DCHECK(cert_buffer_);
   // This would be an absolutely insane number of intermediates.
   if (intermediate_ca_certs_.size() > static_cast<size_t>(INT_MAX) - 1) {
@@ -424,7 +424,7 @@ bool X509Certificate::EqualsIncludingChain(const X509Certificate* other) const {
 }
 
 bool X509Certificate::IsIssuedByEncoded(
-    const std::vector<std::string>& valid_issuers) {
+    const std::vector<std::string>& valid_issuers) const {
   std::vector<std::string> normalized_issuers;
   CertErrors errors;
   for (const auto& raw_issuer : valid_issuers) {

net/cert/x509_certificate.h

@@ -145,7 +145,7 @@ class NET_EXPORT X509Certificate
   // The format is [int count], [data - this certificate],
   // [data - intermediate1], ... [data - intermediateN].
   // All certificates are stored in DER form.
-  void Persist(base::Pickle* pickle);
+  void Persist(base::Pickle* pickle) const;
 
   // The serial number, DER encoded, possibly including a leading 00 byte.
   const std::string& serial_number() const { return serial_number_; }
@@ -189,7 +189,7 @@ class NET_EXPORT X509Certificate
 
   // Do any of the given issuer names appear in this cert's chain of trust?
   // |valid_issuers| is a list of DER-encoded X.509 DistinguishedNames.
-  bool IsIssuedByEncoded(const std::vector<std::string>& valid_issuers);
+  bool IsIssuedByEncoded(const std::vector<std::string>& valid_issuers) const;
 
   // Verifies that |hostname| matches this certificate.
   // Does not verify that the certificate is valid, only that the certificate