mus: Remove the old client lib.

services/ui/public/cpp/window_observer.cc

Index: services/ui/public/cpp/window_observer.cc
diff --git a/services/ui/public/cpp/window_observer.cc b/services/ui/public/cpp/window_observer.cc
deleted file mode 100644
index 796712094bfd5a5dbb3c6050a72efe531fd3edd8..0000000000000000000000000000000000000000
--- a/services/ui/public/cpp/window_observer.cc
+++ /dev/null
@@ -1,18 +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.
-
-#include "services/ui/public/cpp/window_observer.h"
-
-namespace ui {
-
-////////////////////////////////////////////////////////////////////////////////
-// WindowObserver, public:
-
-WindowObserver::TreeChangeParams::TreeChangeParams()
-    : target(nullptr),
-      old_parent(nullptr),
-      new_parent(nullptr),
-      receiver(nullptr) {}
-
-}  // namespace ui