Cleanup after removing views-mus code

ash/mus/window_manager.h

Index: ash/mus/window_manager.h
diff --git a/ash/mus/window_manager.h b/ash/mus/window_manager.h
index 2e561e71d011f1214c084a8a2d16df8c2c2eb13d..1ef3506202645886ad12438d7902ebe1a272673c 100644
--- a/ash/mus/window_manager.h
+++ b/ash/mus/window_manager.h
@@ -33,7 +33,7 @@ class Connector;
 }
 
 namespace views {
-class PointerWatcherEventRouter2;
+class PointerWatcherEventRouter;
 }
 
 namespace wm {
@@ -188,7 +188,7 @@ class WindowManager : public aura::WindowManagerDelegate,
 
   aura::WindowManagerClient* window_manager_client_ = nullptr;
 
-  std::unique_ptr<views::PointerWatcherEventRouter2>
+  std::unique_ptr<views::PointerWatcherEventRouter>
       pointer_watcher_event_router_;
 
   std::unique_ptr<ShadowController> shadow_controller_;