Disable HTTP/2 Alternative Services.

net/http/http_stream_factory_impl_job_controller.cc

Index: net/http/http_stream_factory_impl_job_controller.cc
diff --git a/net/http/http_stream_factory_impl_job_controller.cc b/net/http/http_stream_factory_impl_job_controller.cc
index ec3827716e372fb5e2cbb3acd66e36433f4114aa..a48549074e8720b583b83e430d35e8916130f823 100644
--- a/net/http/http_stream_factory_impl_job_controller.cc
+++ b/net/http/http_stream_factory_impl_job_controller.cc
@@ -950,6 +950,13 @@ HttpStreamFactoryImpl::JobController::GetAlternativeServiceFor(
   }
   UMA_HISTOGRAM_ENUMERATION("Net.AlternativeServiceTypeForRequest", type,
                             MAX_ALTERNATIVE_SERVICE_TYPE);
+
+  // TODO(bnc): https://crbug.com/615413 Re-enable HTTP/2 Alternative Services.
+  if (alternative_service.protocol == kProtoHTTP2 &&
+      !session_->params().enable_http2_alternative_service) {
+    return AlternativeService();
+  }

[Ryan Hamilton, 2017/04/13 21:53:45]

I don't understand why we want to move this here instead of keeping it down in
the loop in GetAlternativeServiceForInternal. Can you say more?

[Bence, 2017/04/14 01:10:16]

Sure.  If it's in GetAlternativeServiceForInternal(), then that never returns an
HTTP/2 alternative service (unless in tests), so
Net.AlternativeServiceTypeForRequest never logs them, so we won't know if they
are advertised in the wild.

[Ryan Hamilton, 2017/04/14 02:49:13]

In that case, perhaps we need a new histogram for rejected AlternativeServices?
I ask because I know that there are server operators planning to advertise both
QUIC and remote H2 so I'd like to make sure that when we encounter those servers
that we speak one of the alternatives.

[Bence, 2017/04/17 11:29:46]

Oops, I wasn't aware of that, sorry.  Let me just revert this part of the change
to make sure that QUIC is used if it is advertised.

+
   return alternative_service;
 }
 
@@ -988,7 +995,6 @@ HttpStreamFactoryImpl::JobController::GetAlternativeServiceForInternal(
       continue;
     }
 
-
     // Some shared unix systems may have user home directories (like
     // http://foo.com/~mike) which allow users to emit headers.  This is a bad
     // idea already, but with Alternate-Protocol, it provides the ability for a
@@ -1002,12 +1008,6 @@ HttpStreamFactoryImpl::JobController::GetAlternativeServiceForInternal(
       continue;
 
     if (alternative_service.protocol == kProtoHTTP2) {
-      if (origin.host() != alternative_service.host &&
-          !session_->params()
-               .enable_http2_alternative_service_with_different_host) {
-        continue;
-      }
-
       // Cache this entry if we don't have a non-broken Alt-Svc yet.
       if (first_alternative_service.protocol == kProtoUnknown)
         first_alternative_service = alternative_service;