Gather metrics classifying the cause of the TLS fallback.

net/http/http_network_transaction.h

Index: net/http/http_network_transaction.h
diff --git a/net/http/http_network_transaction.h b/net/http/http_network_transaction.h
index 09e0a972e7bea6681d6bb68fe79ba4babdf6abb5..5ea399907b1671371204e895995445719dd6abb8 100644
--- a/net/http/http_network_transaction.h
+++ b/net/http/http_network_transaction.h
@@ -22,6 +22,7 @@
 #include "net/proxy/proxy_service.h"
 #include "net/socket/connection_attempts.h"
 #include "net/ssl/ssl_config_service.h"
+#include "net/ssl/ssl_failure_state.h"
 #include "net/websockets/websocket_handshake_stream_base.h"
 
 namespace net {
@@ -85,7 +86,9 @@ class NET_EXPORT_PRIVATE HttpNetworkTransaction
       const SSLConfig& used_ssl_config,
       const ProxyInfo& used_proxy_info,
       WebSocketHandshakeStreamBase* stream) override;
-  void OnStreamFailed(int status, const SSLConfig& used_ssl_config) override;
+  void OnStreamFailed(int status,
+                      const SSLConfig& used_ssl_config,
+                      SSLFailureState ssl_failure_state) override;
   void OnCertificateError(int status,
                           const SSLConfig& used_ssl_config,
                           const SSLInfo& ssl_info) override;
@@ -294,12 +297,16 @@ class NET_EXPORT_PRIVATE HttpNetworkTransaction
 
   SSLConfig server_ssl_config_;
   SSLConfig proxy_ssl_config_;
+  // The SSLFailureState of the most recent failed stream.
+  SSLFailureState server_ssl_failure_state_;
   // fallback_error_code contains the error code that caused the last TLS
   // fallback. If the fallback connection results in
   // ERR_SSL_INAPPROPRIATE_FALLBACK (i.e. the server indicated that the
   // fallback should not have been needed) then we use this value to return the
   // original error that triggered the fallback.
   int fallback_error_code_;
+  // The SSLFailureState which caused the last TLS version fallback.
+  SSLFailureState fallback_failure_state_;
 
   HttpRequestHeaders request_headers_;