Only record fallback metrics on successful requests.

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 a3a9ef77fe613755152530d35d079da5ef6c2d08..09e0a972e7bea6681d6bb68fe79ba4babdf6abb5 100644
--- a/net/http/http_network_transaction.h
+++ b/net/http/http_network_transaction.h
@@ -235,6 +235,9 @@ class NET_EXPORT_PRIVATE HttpNetworkTransaction
   // to be maintained for multi-round auth.
   void ResetStateForAuthRestart();
 
+  // Records metrics relating to SSL fallbacks.
+  void RecordSSLFallbackMetrics();
+
   // Returns true if we should try to add a Proxy-Authorization header
   bool ShouldApplyProxyAuth() const;