QUIC - added force_hol_blocking field trial param to enable forced HOL blocking.

net/quic/quic_stream_factory.cc

Index: net/quic/quic_stream_factory.cc
diff --git a/net/quic/quic_stream_factory.cc b/net/quic/quic_stream_factory.cc
index 832cf909eb8a9ff21ccacd572ab8e25feb7eac82..56fc8a1f4703b9f9b7c75c4c0c7f6e75d70d9097 100644
--- a/net/quic/quic_stream_factory.cc
+++ b/net/quic/quic_stream_factory.cc
@@ -632,6 +632,7 @@ QuicStreamFactory::QuicStreamFactory(
     int idle_connection_timeout_seconds,
     bool migrate_sessions_on_network_change,
     bool migrate_sessions_early,
+    bool force_hol_blocking,
     const QuicTagVector& connection_options,
     bool enable_token_binding)
     : require_confirmation_(true),
@@ -685,6 +686,7 @@ QuicStreamFactory::QuicStreamFactory(
           NetworkChangeNotifier::AreNetworkHandlesSupported()),
       migrate_sessions_early_(migrate_sessions_early &&
                               migrate_sessions_on_network_change_),
+      force_hol_blocking_(force_hol_blocking),
       port_seed_(random_generator_->RandUint64()),
       check_persisted_supports_quic_(true),
       has_initialized_data_(false),
@@ -1676,6 +1678,10 @@ int QuicStreamFactory::CreateSession(
     config.SetInitialRoundTripTimeUsToSend(static_cast<uint32_t>(srtt));
   config.SetBytesForConnectionIdToSend(0);
 
+  if (force_hol_blocking_) {
+    config.SetForceHolBlocking();

[Ryan Hamilton, 2016/07/01 21:32:27]

Can we add a test to quic_stream_factory_test that the created sessions' config
has this set?

We should probably also have a test in quic_network_transaction_tests which
shows this happening. Probably a post body?

[Buck, 2016/07/08 22:17:09]

Done.

+  }

[Ryan Hamilton, 2016/07/01 21:32:27]

nit: no {}s on 1-line ifs in net/ code.

[Buck, 2016/07/08 22:17:09]

Done.

+
   if (quic_server_info_factory_.get() && !server_info) {
     // Start the disk cache loading so that we can persist the newer QUIC server
     // information and/or inform the disk cache that we have reused