Update from https://crrev.com/308331

net/ssl/client_cert_store.h

 // Copyright (c) 2012 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.
 
 #ifndef NET_SSL_CLIENT_CERT_STORE_H_
 #define NET_SSL_CLIENT_CERT_STORE_H_
 
 #include "base/basictypes.h"
 #include "base/callback_forward.h"
 #include "net/base/net_export.h"
 #include "net/cert/x509_certificate.h"
 
 namespace net {
 
 class SSLCertRequestInfo;
 
-// The caller is expected to keep the ClientCertStore alive until the callback
-// supplied to GetClientCerts has been run.
+// A handle to a client certificate store to query matching certificates when a
+// server requests client auth. Note that there may be multiple ClientCertStore
+// objects corresponding to the same platform certificate store; each request
+// gets its own uniquely owned handle.
 class NET_EXPORT ClientCertStore {
  public:
   virtual ~ClientCertStore() {}
 
   // Get client certs matching the |cert_request_info|. On completion, the
   // results will be stored in |selected_certs| and the |callback| will be run.
   // The |callback| may be called sychronously. The caller must ensure the
-  // ClientCertStore and the |selected_certs| object remain alive until the
-  // callback has been run.
+  // ClientCertStore, |cert_request_info|, and |selected_certs| remain alive
+  // until the callback has been run.
   virtual void GetClientCerts(const SSLCertRequestInfo& cert_request_info,
                               CertificateList* selected_certs,
                               const base::Closure& callback) = 0;
  protected:
   ClientCertStore() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ClientCertStore);
 };
 
 }  // namespace net
 
 #endif  // NET_SSL_CLIENT_CERT_STORE_H_