Make HttpNetworkSession::host_mapping_rules no longer a pointer.

chrome/browser/io_thread.cc

Index: chrome/browser/io_thread.cc
diff --git a/chrome/browser/io_thread.cc b/chrome/browser/io_thread.cc
index 71e11962e31cbbe6c5a95404fdd6d3cb65d06d97..5ddeda3603871a211062362972619a4ffb450b0f 100644
--- a/chrome/browser/io_thread.cc
+++ b/chrome/browser/io_thread.cc
@@ -644,15 +644,15 @@ void IOThread::Init() {
       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 =