mus: Remove the old client lib.

services/ui/public/cpp/window_tracker.h

Index: services/ui/public/cpp/window_tracker.h
diff --git a/services/ui/public/cpp/window_tracker.h b/services/ui/public/cpp/window_tracker.h
deleted file mode 100644
index ef221fd94ea15154dc8b90f8fbf99783df14202a..0000000000000000000000000000000000000000
--- a/services/ui/public/cpp/window_tracker.h
+++ /dev/null
@@ -1,21 +0,0 @@
-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef SERVICES_UI_PUBLIC_CPP_WINDOW_TRACKER_H_
-#define SERVICES_UI_PUBLIC_CPP_WINDOW_TRACKER_H_
-
-#include <stdint.h>
-#include <set>
-
-#include "base/macros.h"
-#include "services/ui/public/cpp/window_observer.h"
-#include "ui/base/window_tracker_template.h"
-
-namespace ui {
-
-using WindowTracker = ui::WindowTrackerTemplate<Window, WindowObserver>;
-
-}  // namespace ui
-
-#endif  // SERVICES_UI_PUBLIC_CPP_WINDOW_TRACKER_H_