Use base::MessageLoopProxy instead of MessageLoop in ProxyConfigServiceLinux.

net/proxy/proxy_service.cc

Index: net/proxy/proxy_service.cc
diff --git a/net/proxy/proxy_service.cc b/net/proxy/proxy_service.cc
index 39638e24134981caa5ad145b96b2b424064b5010..6df9ce9adf30a6b62e29c0539b7c5dacfab1dd21 100644
--- a/net/proxy/proxy_service.cc
+++ b/net/proxy/proxy_service.cc
@@ -1424,7 +1424,9 @@ ProxyConfigService* ProxyService::CreateSystemProxyConfigService(
   // running on glib_default_loop). Additionally register for
   // notifications (delivered in either |glib_default_loop| or
   // |file_loop|) to keep us updated when the proxy config changes.
-  linux_config_service->SetupAndFetchInitialConfig(glib_default_loop, io_loop,
+  linux_config_service->SetupAndFetchInitialConfig(
+      glib_default_loop->message_loop_proxy(),
+      io_loop->message_loop_proxy(),
       static_cast<MessageLoopForIO*>(file_loop));
 
   return linux_config_service;