Revert of base: Remove use of MessageLoopProxy

base/win/object_watcher.cc

Index: base/win/object_watcher.cc
diff --git a/base/win/object_watcher.cc b/base/win/object_watcher.cc
index 5ebe1856d3182aec93dd97e08f712f761d5bbbf9..35609fcf5c39b2aac015c95ff196f410543be162 100644
--- a/base/win/object_watcher.cc
+++ b/base/win/object_watcher.cc
@@ -92,7 +92,7 @@
   // The destructor blocks on any callbacks that are in flight, so we know that
   // that is always a pointer to a valid ObjectWater.
   ObjectWatcher* that = static_cast<ObjectWatcher*>(param);
-  that->origin_loop_->task_runner()->PostTask(FROM_HERE, that->callback_);
+  that->origin_loop_->PostTask(FROM_HERE, that->callback_);
   that->callback_.Reset();
 }