Mac: implement <keygen> support, including adding generated cert to the Keychain.

net/url_request/url_request.h

Index: net/url_request/url_request.h
diff --git a/net/url_request/url_request.h b/net/url_request/url_request.h
index c8bc2bf8079613e22b647fe786ae4e251c23970c..9dcc3c9016f18125ccd4b04371eaa50d058c5559 100644
--- a/net/url_request/url_request.h
+++ b/net/url_request/url_request.h
@@ -187,6 +187,14 @@ class URLRequest {
       request->Cancel();
     }
 
+    // Called when the server response body contains a client certificate to be
+    // stored locally. This happens in response to the posting of a form that
+    // contains a <keygen> element -- the server fills out the certificate
+    // request and returns the X.509 cert data.
+    virtual void OnClientCertificateGenerated(URLRequest* request,
+                                              net::X509Certificate* cert) {
+    }
+
     // Called when unable to get cookies due to policy.
     virtual void OnGetCookiesBlocked(URLRequest* request) {
     }