Make HttpNetworkSession::host_mapping_rules no longer a pointer.

chrome/browser/io_thread.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 "chrome/browser/io_thread.h"
 
 #include <utility>
 #include <vector>
 
 #include "base/base64.h"
@@ skipping 626 matching lines @@
 
   globals_->ssl_config_service = GetSSLConfigService();
 
   CreateDefaultAuthHandlerFactory();
   globals_->http_server_properties.reset(new net::HttpServerPropertiesImpl());
   // For the ProxyScriptFetcher, we use a direct ProxyService.
   globals_->proxy_script_fetcher_proxy_service =
       net::ProxyService::CreateDirectWithNetLog(net_log_);
   globals_->dns_probe_service.reset(new chrome_browser_net::DnsProbeService());
   globals_->host_mapping_rules.reset(new net::HostMappingRules());
-  params_.host_mapping_rules = globals_->host_mapping_rules.get();
-  globals_->http_user_agent_settings.reset(
-      new net::StaticHttpUserAgentSettings(std::string(), GetUserAgent()));

[Randy Smith (Not in Mondays), 2017/05/25 17:50:48]

Why move this line?  (I don't care, I'm just worried there's a data dependency
I'm not seeing.)

[mmenke, 2017/05/25 18:07:10]

Purely for code hygiene resions.  It's weird to have:

I moved UserAgentSettings because it's weird to have:

<Do some HostMapping setup>
<Set up UserAgentSettings>
<Finish HostMapping setup>

I moved params_.host_mapping_rules initialization because I had to - before, it
was copying a pointer, so it was fine to configure
globals_->host_mapping_rules.get() after setting params_.host_mapping_rules. 
However, now that we're copying the contents of the rules instead of just using
a pointer to them, the global one ha to be configured first.

[Randy Smith (Not in Mondays), 2017/05/25 18:17:06]

Understood; that's fine. 

(I understood moving the host mapping rules; it was the user agent stuff I
wanted to make sure I wasn't missing anything on.)

   if (command_line.HasSwitch(switches::kHostRules)) {
     TRACE_EVENT_BEGIN0("startup", "IOThread::InitAsync:SetRulesFromString");
     globals_->host_mapping_rules->SetRulesFromString(
         command_line.GetSwitchValueASCII(switches::kHostRules));
     TRACE_EVENT_END0("startup", "IOThread::InitAsync:SetRulesFromString");
   }
+  params_.host_mapping_rules = *globals_->host_mapping_rules.get();
+  globals_->http_user_agent_settings.reset(
+      new net::StaticHttpUserAgentSettings(std::string(), GetUserAgent()));
   globals_->enable_brotli =
       base::FeatureList::IsEnabled(features::kBrotliEncoding);
   params_.enable_token_binding =
       base::FeatureList::IsEnabled(features::kTokenBinding);
 
   // Check for OS support of TCP FastOpen, and turn it on for all connections if
   // indicated by user.
   // TODO(rch): Make the client socket factory a per-network session instance,
   // constructed from a NetworkSession::Params, to allow us to move this option
   // to IOThread::Globals & HttpNetworkSession::Params.
@@ skipping 428 matching lines @@
 
   // TODO(rtenneti): We should probably use HttpServerPropertiesManager for the
   // system URLRequestContext too. There's no reason this should be tied to a
   // profile.
   return context;
 }
 
 metrics::UpdateUsagePrefCallbackType IOThread::GetMetricsDataUseForwarder() {
   return base::Bind(&UpdateMetricsUsagePrefsOnUIThread);
 }