net: add DNS certificate revocation experiment.

net/url_request/url_request_context.h

Index: net/url_request/url_request_context.h
diff --git a/net/url_request/url_request_context.h b/net/url_request/url_request_context.h
index 7d9d2e6085577888a7d76a1740ab6caf7e56575b..489ac22f591e5061c0f0805cd8b4aa4cd95c259e 100644
--- a/net/url_request/url_request_context.h
+++ b/net/url_request/url_request_context.h
@@ -25,6 +25,7 @@
 namespace net {
 class CertVerifier;
 class CookieStore;
+class DnsRRResolver;
 class FraudulentCertificateReporter;
 class FtpTransactionFactory;
 class HostResolver;
@@ -189,6 +190,8 @@ class NET_EXPORT URLRequestContext
     job_factory_ = job_factory;
   }
 
+  DnsRRResolver* dnsrr_resolver() const { return dnsrr_resolver_.get(); }
+
  protected:
   friend class base::RefCountedThreadSafe<URLRequestContext>;
 
@@ -226,6 +229,7 @@ class NET_EXPORT URLRequestContext
   HttpTransactionFactory* http_transaction_factory_;
   FtpTransactionFactory* ftp_transaction_factory_;
   const URLRequestJobFactory* job_factory_;
+  scoped_ptr<DnsRRResolver> dnsrr_resolver_;
 
   // ---------------------------------------------------------------------------
   // Important: When adding any new members below, consider whether they need to