Converts WindowTreeClientTest to be in terms of aura

services/ui/test_wm/test_wm.cc

Index: services/ui/test_wm/test_wm.cc
diff --git a/services/ui/test_wm/test_wm.cc b/services/ui/test_wm/test_wm.cc
index ed0d1e795a341942395fc660445146da06a06de0..52f31de3730096f80908d6ce47facee0fd688247 100644
--- a/services/ui/test_wm/test_wm.cc
+++ b/services/ui/test_wm/test_wm.cc
@@ -85,7 +85,8 @@ class TestWM : public service_manager::Service,
     window_tree_host_.reset();
     window_tree_client_.reset();
   }
-  void OnEmbedRootDestroyed(aura::Window* root) override {
+  void OnEmbedRootDestroyed(
+      aura::WindowTreeHostMus* window_tree_host) override {
     // WindowTreeClients configured as the window manager should never get
     // OnEmbedRootDestroyed().
     NOTREACHED();