net: add DNS certificate revocation experiment.

net/url_request/url_request_context.cc

Index: net/url_request/url_request_context.cc
diff --git a/net/url_request/url_request_context.cc b/net/url_request/url_request_context.cc
index c2c784334cdccdd49894e6c3ab66e2cfaac50cb1..7ee6e34793d4e5f16d10a78994ba856e65015bf0 100644
--- a/net/url_request/url_request_context.cc
+++ b/net/url_request/url_request_context.cc
@@ -6,6 +6,7 @@
 
 #include "base/compiler_specific.h"
 #include "base/string_util.h"
+#include "net/base/dnsrr_resolver.h"
 #include "net/base/host_resolver.h"
 #include "net/cookies/cookie_store.h"
 #include "net/ftp/ftp_transaction_factory.h"
@@ -28,7 +29,8 @@ URLRequestContext::URLRequestContext()
       ftp_auth_cache_(new FtpAuthCache),
       http_transaction_factory_(NULL),
       ftp_transaction_factory_(NULL),
-      job_factory_(NULL) {
+      job_factory_(NULL),
+      dnsrr_resolver_(new DnsRRResolver) {
 }
 
 void URLRequestContext::CopyFrom(URLRequestContext* other) {