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

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 e48985d2ef323b1bba210ba73b29e604b6ee6b6e..b13e3c63365ef3b2d34e56ab0fc7a9762d33b0b0 100644
--- a/net/quic/quic_stream_factory.cc
+++ b/net/quic/quic_stream_factory.cc
@@ -27,7 +27,6 @@
 #include "net/cert/ct_verifier.h"
 #include "net/dns/host_resolver.h"
 #include "net/dns/single_request_host_resolver.h"
-#include "net/http/http_server_properties.h"
 #include "net/quic/crypto/channel_id_chromium.h"
 #include "net/quic/crypto/proof_verifier_chromium.h"
 #include "net/quic/crypto/properties_based_quic_server_info.h"
@@ -710,6 +709,20 @@ void QuicStreamFactory::set_quic_server_info_factory(
   quic_server_info_factory_.reset(quic_server_info_factory);
 }
 
+bool QuicStreamFactory::CanUseExistingSession(QuicServerId server_id,
+                                              PrivacyMode privacy_mode,
+                                              StringPiece origin_host) {
+  // TODO(zhongyi): delete active_sessions_.empty() checks once the
+  // android crash issue(crbug.com/498823) is resolved.
+  if (active_sessions_.empty())
+    return false;
+  SessionMap::iterator it = active_sessions_.find(server_id);
+  if (it == active_sessions_.end())
+    return false;
+  QuicChromiumClientSession* session = it->second;
+  return session->CanPool(origin_host.as_string(), privacy_mode);
+}
+
 int QuicStreamFactory::Create(const HostPortPair& host_port_pair,
                               PrivacyMode privacy_mode,
                               int cert_verify_flags,