Mandoline UI Process: Update namespaces and file names

components/mus/public/cpp/lib/view_observer.cc

 // 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 "components/mus/public/cpp/view_observer.h"
 
-namespace mojo {
+namespace mus {
 
 ////////////////////////////////////////////////////////////////////////////////
 // ViewObserver, public:
 
 ViewObserver::TreeChangeParams::TreeChangeParams()
     : target(nullptr),
       old_parent(nullptr),
       new_parent(nullptr),
       receiver(nullptr) {}
 
-}  // namespace mojo
+}  // namespace mus