Changes how window manager obtains WindowTree from mus

components/mus/ws/window_manager_client_unittest.cc

Index: components/mus/ws/window_manager_client_unittest.cc
diff --git a/components/mus/ws/window_manager_client_unittest.cc b/components/mus/ws/window_manager_client_unittest.cc
index 1721a4d96473247140b5675fa0db8e57b92dace5..a8049c6b69bcf72b5676873629f747c454ffc038 100644
--- a/components/mus/ws/window_manager_client_unittest.cc
+++ b/components/mus/ws/window_manager_client_unittest.cc
@@ -60,6 +60,8 @@ class TestWindowManagerDelegate : public WindowManagerDelegate {
   }
   void OnWmClientJankinessChanged(const std::set<Window*>& client_windows,
                                   bool janky) override {}
+  void OnWmNewDisplay(Window* window,
+                      const display::Display& display) override {}
   void OnAccelerator(uint32_t id, const ui::Event& event) override {}
 
  private: