Always run PolicyWatcher on UI thread in It2Me host.

remoting/host/policy_hack/policy_watcher_unittest.cc

Index: remoting/host/policy_hack/policy_watcher_unittest.cc
diff --git a/remoting/host/policy_hack/policy_watcher_unittest.cc b/remoting/host/policy_hack/policy_watcher_unittest.cc
index a04fe87a1e0260bbebeab4bb1ed280543bc904b8..f01b042a96688dc29fb2d6a952f64ce091e10a50 100644
--- a/remoting/host/policy_hack/policy_watcher_unittest.cc
+++ b/remoting/host/policy_hack/policy_watcher_unittest.cc
@@ -555,7 +555,7 @@ TEST_F(PolicyWatcherTest, TestRealChromotingPolicy) {
   scoped_refptr<base::SingleThreadTaskRunner> task_runner =
       base::MessageLoop::current()->task_runner();
   scoped_ptr<PolicyWatcher> policy_watcher(
-      PolicyWatcher::Create(nullptr, task_runner));
+      PolicyWatcher::Create(nullptr, task_runner, task_runner));
 
   {
     base::RunLoop run_loop;