Implement nextHopProtocol in PerformanceResourceTiming and PerformanceNavigationTiming.

content/public/renderer/document_state.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/public/renderer/document_state.h"
 
 #include "content/public/renderer/navigation_state.h"
 
 namespace content {
 
 DocumentState::DocumentState()
     : was_fetched_via_spdy_(false),
       was_alpn_negotiated_(false),
       was_alternate_protocol_available_(false),
-      connection_info_(net::HttpResponseInfo::CONNECTION_INFO_UNKNOWN),
+      connection_info_(net::HttpResponseInfo::ConnectionInfoToString(
+          net::HttpResponseInfo::CONNECTION_INFO_UNKNOWN)),
       was_load_data_with_base_url_request_(false),
       can_load_local_resources_(false) {}
 
 DocumentState::~DocumentState() {}
 
 void DocumentState::set_navigation_state(NavigationState* navigation_state) {
   navigation_state_.reset(navigation_state);
 }
 
 }  // namespace content