Explicitly make BrowserThread::SetDelegate specific to the IO thread.

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 416 matching lines @@
   value = policy_service
               ->GetPolicies(policy::PolicyNamespace(
                   policy::POLICY_DOMAIN_CHROME, std::string()))
               .GetValue(policy::key::kHttp09OnNonDefaultPortsEnabled);
   if (value)
     value->GetAsBoolean(&http_09_on_non_default_ports_enabled_);
 
   chrome_browser_net::SetGlobalSTHDistributor(
       std::unique_ptr<net::ct::STHDistributor>(new net::ct::STHDistributor()));
 
-  BrowserThread::SetDelegate(BrowserThread::IO, this);
+  BrowserThread::SetIOThreadDelegate(this);
 }
 
 IOThread::~IOThread() {
   // This isn't needed for production code, but in tests, IOThread may
   // be multiply constructed.
-  BrowserThread::SetDelegate(BrowserThread::IO, NULL);
+  BrowserThread::SetIOThreadDelegate(nullptr);
 
   pref_proxy_config_tracker_->DetachFromPrefService();
   DCHECK(!globals_);
 
   // Destroy the old distributor to check that the observers list it holds is
   // empty.
   chrome_browser_net::SetGlobalSTHDistributor(nullptr);
 }
 
 IOThread::Globals* IOThread::globals() {
@@ skipping 634 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);
 }