Discard SSL certificates for non-committed entries to save memory.

content/public/browser/ssl_status.h

Index: content/public/browser/ssl_status.h
diff --git a/content/public/browser/ssl_status.h b/content/public/browser/ssl_status.h
index fe648b4226c24eb8194d211ad01dea0806394299..73f708098e7cc53b414bc8759fb16f173dcbdb98 100644
--- a/content/public/browser/ssl_status.h
+++ b/content/public/browser/ssl_status.h
@@ -74,6 +74,9 @@ struct CONTENT_EXPORT SSLStatus {
   }
 
   bool initialized;
+  // Note: this is only valid for committed entries. For other entries in the
+  // NavigationController (e.g. previous entries) we prune the certificate to
+  // save memory.
   scoped_refptr<net::X509Certificate> certificate;
   net::CertStatus cert_status;
   int security_bits;