Get ClientCertStore through ResourceContext.

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.
 class NET_EXPORT ClientCertStore {
  public:
   virtual ~ClientCertStore() {}
 
-  virtual bool GetClientCerts(const SSLCertRequestInfo& cert_request_info,
-                              CertificateList* selected_certs) = 0;
+  // Get client certs matching the |cert_request_info|.  The |callback| may be
+  // called sychronously.
+  virtual void GetClientCerts(const SSLCertRequestInfo& cert_request_info,
+                              CertificateList* selected_certs,
+                              const base::Closure& callback) = 0;

[wtc, 2013/10/28 19:41:12]

Nit: If I only look at this interface and its comments, I won't know how the
method works in synchronous and asynchronous modes.

Two things are unclear to me.

1. What happens to selected_certs. In particular, what happens to selected_certs
in asynchronous mode.

2. When will |callback| be called.

[mattm, 2013/10/28 23:56:16]

Expanded the comment

  protected:
   ClientCertStore() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ClientCertStore);
 };
 
 }  // namespace net
 
 #endif  // NET_SSL_CLIENT_CERT_STORE_H_