Remove remaining calls to deprecated MessageLoop methods on Mac.

base/files/file_path_watcher_unittest.cc

Index: base/files/file_path_watcher_unittest.cc
diff --git a/base/files/file_path_watcher_unittest.cc b/base/files/file_path_watcher_unittest.cc
index a40e4858b4bea7d70a0f25896d3d162dbeafa329..22041e215235473793ae5dacfe773cb30b78fb1f 100644
--- a/base/files/file_path_watcher_unittest.cc
+++ b/base/files/file_path_watcher_unittest.cc
@@ -197,9 +197,9 @@ class FilePathWatcherTest : public testing::Test {
   bool WaitForEvents() WARN_UNUSED_RESULT {
     collector_->Reset();
     // Make sure we timeout if we don't get notified.
-    loop_.PostDelayedTask(FROM_HERE,
-                          MessageLoop::QuitWhenIdleClosure(),
-                          TestTimeouts::action_timeout());
+    loop_.task_runner()->PostDelayedTask(FROM_HERE,
+                                         MessageLoop::QuitWhenIdleClosure(),
+                                         TestTimeouts::action_timeout());
     RunLoop().Run();
     return collector_->Success();
   }