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..fbf19041fb80013c7bda8d32f206ac16b8e84d1d 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 +148,11 @@ class NET_EXPORT_PRIVATE QuicStreamFactory
       const QuicTagVector& connection_options);
   ~QuicStreamFactory() override;
 
+  // Returns true if a matching session already exists.

[Ryan Hamilton, 2015/12/18 17:52:51]

I might say something like:

// Returns true if there is an existing session to |server_id| which can be used
for requests to |origin_host|.

[Zhongyi Shi, 2015/12/18 21:59:29]

Done.

+  bool CanPool(HostPortPair host_port_pair,
+               PrivacyMode privacy_mode,

[Ryan Hamilton, 2015/12/18 17:52:51]

Your call, but I would make this take a QuicServerId

[Zhongyi Shi, 2015/12/18 21:59:29]

Done.

+               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