Make aura work with mus

ui/aura/mus/window_tree_client_observer.h

Index: ui/aura/mus/window_tree_client_observer.h
diff --git a/services/ui/public/cpp/window_tree_client_observer.h b/ui/aura/mus/window_tree_client_observer.h
similarity index 55%
copy from services/ui/public/cpp/window_tree_client_observer.h
copy to ui/aura/mus/window_tree_client_observer.h
index 16d7082548d4af79d9d3bd46427ed3e03aeb09ca..9ecc3f8f3642e29fc95a0772322fea8dd6733cf7 100644
--- a/services/ui/public/cpp/window_tree_client_observer.h
+++ b/ui/aura/mus/window_tree_client_observer.h
@@ -2,22 +2,18 @@
 // 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_TREE_CLIENT_OBSERVER_H_
-#define SERVICES_UI_PUBLIC_CPP_WINDOW_TREE_CLIENT_OBSERVER_H_
+#ifndef UI_AURA_MUS_WINDOW_TREE_CLIENT_OBSERVER_H_
+#define UI_AURA_MUS_WINDOW_TREE_CLIENT_OBSERVER_H_
 
-namespace ui {
+#include "ui/aura/aura_export.h"
+
+namespace aura {
 
 class Window;
 class WindowTreeClient;
 
-class WindowTreeClientObserver {
+class AURA_EXPORT WindowTreeClientObserver {
  public:
-  virtual void OnWindowTreeFocusChanged(Window* gained_focus,
-                                        Window* lost_focus) {}
-
-  virtual void OnWindowTreeCaptureChanged(Window* gained_capture,
-                                          Window* lost_capture) {}
-
   // Called early on in the destructor of WindowTreeClient; before any windows
   // have been destroyed.
   virtual void OnWillDestroyClient(WindowTreeClient* client) {}
@@ -30,6 +26,6 @@ class WindowTreeClientObserver {
   virtual ~WindowTreeClientObserver() {}
 };
 
-}  // namespace ui
+}  // namespace aura
 
-#endif  // SERVICES_UI_PUBLIC_CPP_WINDOW_TREE_CLIENT_OBSERVER_H_
+#endif  // UI_AURA_MUS_WINDOW_TREE_CLIENT_OBSERVER_H_