ScopedTrackers to help pin down where IOThread::InitSystemRequestContextOnIOThread is janky

chrome/browser/net/proxy_service_factory.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/net/proxy_service_factory.h"
 
 #include "base/command_line.h"
+#include "base/profiler/scoped_tracker.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/threading/thread.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/io_thread.h"
 #include "chrome/browser/net/pref_proxy_config_tracker_impl.h"
 #include "chrome/common/chrome_switches.h"
 #include "content/public/browser/browser_thread.h"
 #include "net/base/net_log.h"
 #include "net/proxy/dhcp_proxy_script_fetcher_factory.h"
 #include "net/proxy/proxy_config_service.h"
@@ skipping 69 matching lines @@
 // static
 net::ProxyService* ProxyServiceFactory::CreateProxyService(
     net::NetLog* net_log,
     net::URLRequestContext* context,
     net::NetworkDelegate* network_delegate,
     net::ProxyConfigService* proxy_config_service,
     const base::CommandLine& command_line,
     bool quick_check_enabled) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 
+  // TODO(michaeln): Remove ScopedTracker below once crbug.com/454983 is fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "454983 ProxyServiceFactory::CreateProxyService"));
+
 #if defined(OS_IOS)
   bool use_v8 = false;
 #else
   bool use_v8 = !command_line.HasSwitch(switches::kWinHttpProxyResolver);
   if (use_v8 && command_line.HasSwitch(switches::kSingleProcess)) {
     // See the note about V8 multithreading in net/proxy/proxy_resolver_v8.h
     // to understand why we have this limitation.
     LOG(ERROR) << "Cannot use V8 Proxy resolver in single process mode.";
     use_v8 = false;  // Fallback to non-v8 implementation.
   }
@@ skipping 43 matching lines @@
     proxy_service = net::ProxyService::CreateUsingSystemProxyResolver(
         proxy_config_service,
         num_pac_threads,
         net_log);
   }
 
   proxy_service->set_quick_check_enabled(quick_check_enabled);
 
   return proxy_service;
 }