Remove remaining calls to deprecated MessageLoop methods.

remoting/host/ipc_desktop_environment_unittest.cc

Index: remoting/host/ipc_desktop_environment_unittest.cc
diff --git a/remoting/host/ipc_desktop_environment_unittest.cc b/remoting/host/ipc_desktop_environment_unittest.cc
index c7965f2e273a1b06f62e2aafdc37563967b422f3..d256e8531305b388f34c05ed0703ed653564d155 100644
--- a/remoting/host/ipc_desktop_environment_unittest.cc
+++ b/remoting/host/ipc_desktop_environment_unittest.cc
@@ -18,6 +18,7 @@
 #include "base/process/process.h"
 #include "base/process/process_handle.h"
 #include "base/run_loop.h"
+#include "base/single_thread_task_runner.h"
 #include "build/build_config.h"
 #include "ipc/attachment_broker_privileged.h"
 #include "ipc/ipc_channel.h"
@@ -374,7 +375,8 @@ DesktopEnvironment* IpcDesktopEnvironmentTest::CreateDesktopEnvironment() {
       .Times(AtMost(1));
 
   // Let tests know that the remote desktop environment is created.
-  message_loop_.PostTask(FROM_HERE, setup_run_loop_->QuitClosure());
+  message_loop_.task_runner()->PostTask(FROM_HERE,
+                                        setup_run_loop_->QuitClosure());
 
   return desktop_environment;
 }