Add a whitelist for QUIC hosts.

net/http/http_network_session.h

Index: net/http/http_network_session.h
diff --git a/net/http/http_network_session.h b/net/http/http_network_session.h
index c75d85f08708da563d3656e851fed59e6c0b8eda..5b1ecf40d298e966d2dceea45a9b3f36d30283c7 100644
--- a/net/http/http_network_session.h
+++ b/net/http/http_network_session.h
@@ -10,6 +10,7 @@
 
 #include <set>
 #include <string>
+#include <unordered_set>
 #include <vector>
 
 #include "base/memory/ref_counted.h"
@@ -181,6 +182,9 @@ class NET_EXPORT HttpNetworkSession
     int quic_idle_connection_timeout_seconds;
     // If true, disable preconnections if QUIC can do 0RTT.
     bool quic_disable_preconnect_if_0rtt;
+    // List of hosts for which QUIC is explicitly whitelisted.
+    std::unordered_set<std::string> quic_host_whitelist;
+
     ProxyDelegate* proxy_delegate;
   };