Change the interface of GetAlternativeServicesFor, always return the best Alt-Svc entry.

net/quic/quic_stream_factory.h

Index: net/quic/quic_stream_factory.h
diff --git a/net/quic/quic_stream_factory.h b/net/quic/quic_stream_factory.h
index 644fbc7672759f5b809969401dce63b47389c064..028aef8f082517ae6a9ac0d5f7173016ae8e4472 100644
--- a/net/quic/quic_stream_factory.h
+++ b/net/quic/quic_stream_factory.h
@@ -19,6 +19,7 @@
 #include "net/base/host_port_pair.h"
 #include "net/base/network_change_notifier.h"
 #include "net/cert/cert_database.h"
+#include "net/http/http_server_properties.h"
 #include "net/log/net_log.h"
 #include "net/proxy/proxy_server.h"
 #include "net/quic/network_connection.h"
@@ -147,6 +148,12 @@ class NET_EXPORT_PRIVATE QuicStreamFactory
       const QuicTagVector& connection_options);
   ~QuicStreamFactory() override;
 
+  // Returns true if there is an existing session to |server_id| which can be
+  // for request to |origin_host|.
+  bool CanPool(QuicServerId server_id,

[Ryan Hamilton, 2015/12/18 22:56:29]

How about |CanUseExistingSession| or some such. Because server_id.host might ==
origing_host, in which case it's not pooling.

[Zhongyi Shi, 2015/12/19 01:23:02]

Done.

+               PrivacyMode privacy_mode,

[Ryan Hamilton, 2015/12/18 22:56:29]

I think you can remove this arg.

[Zhongyi Shi, 2015/12/19 01:23:02]

Unfortunately, we can't. We still need privacy_mode when call
QuicChromiumClientSession::CanPool though we are passing in the QuicServerId. 

+               StringPiece origin_host);
+
   // Creates a new QuicHttpStream to |host_port_pair| which will be
   // owned by |request|.
   // If a matching session already exists, this method will return OK.  If no