Move ProxyConfigService construction onto the IO thread.

net/proxy/proxy_service.h

Index: net/proxy/proxy_service.h
diff --git a/net/proxy/proxy_service.h b/net/proxy/proxy_service.h
index 3d894202591e5b016742551cf4afaf806fa24909..3ac4be33c948c66b289bdbfdf1a93560491861a4 100644
--- a/net/proxy/proxy_service.h
+++ b/net/proxy/proxy_service.h
@@ -201,6 +201,9 @@ class NET_EXPORT ProxyService : public NetworkChangeNotifier::IPAddressObserver,
   // to downloading and testing the PAC files.
   void ForceReloadProxyConfig();
 
+  // Give ProxyConfigService a chance to perform shutdown work.
+  void StartTearDown();
+
   // Same as CreateProxyServiceUsingV8ProxyResolver, except it uses system
   // libraries for evaluating the PAC script if available, otherwise skips
   // proxy autoconfig.
@@ -234,7 +237,7 @@ class NET_EXPORT ProxyService : public NetworkChangeNotifier::IPAddressObserver,
   // Creates a config service appropriate for this platform that fetches the
   // system proxy settings.
   static ProxyConfigService* CreateSystemProxyConfigService(
-      base::SingleThreadTaskRunner* io_thread_task_runner,
+      base::SingleThreadTaskRunner* glib_thread_task_runner,
       MessageLoop* file_loop);
 
   // This method should only be used by unit tests.