Use SingleThreadTaskRunner instead of MessageLoopProxy in remoting/host.

remoting/host/url_fetcher_unittest.cc

Index: remoting/host/url_fetcher_unittest.cc
diff --git a/remoting/host/url_fetcher_unittest.cc b/remoting/host/url_fetcher_unittest.cc
index 811fe419592b116ea525001874850660fc708298..3c1c3f27ac47decddd731594cf9b2dad284f9e1e 100644
--- a/remoting/host/url_fetcher_unittest.cc
+++ b/remoting/host/url_fetcher_unittest.cc
@@ -33,7 +33,7 @@ class UrlFetcherTest : public testing::Test  {
         base::Thread::Options(MessageLoop::TYPE_IO, 0)));
     context_getter_ = new URLRequestContextGetter(
         message_loop_.message_loop_proxy(),
-        io_thread_.message_loop(),
+        io_thread_.message_loop_proxy(),
         static_cast<MessageLoopForIO*>(file_thread_.message_loop()));
     ASSERT_TRUE(test_server_.Start());
   }