exo: Run exo in mus+ash

chrome/browser/chrome_browser_main_extra_parts_exo.h

Index: chrome/browser/chrome_browser_main_extra_parts_exo.h
diff --git a/chrome/browser/chrome_browser_main_extra_parts_exo.h b/chrome/browser/chrome_browser_main_extra_parts_exo.h
index 8fc5f060dd8ee57452dd6e3e53f992d1c86e4376..7e97f85d8065ee5cf2901ad29a625265c223c8da 100644
--- a/chrome/browser/chrome_browser_main_extra_parts_exo.h
+++ b/chrome/browser/chrome_browser_main_extra_parts_exo.h
@@ -12,6 +12,7 @@
 
 namespace exo {
 class Display;
+class WMHelper;
 namespace wayland {
 class Server;
 }
@@ -33,6 +34,7 @@ class ChromeBrowserMainExtraPartsExo : public ChromeBrowserMainExtraParts {
  private:
   std::unique_ptr<arc::ArcNotificationSurfaceManager>
       arc_notification_surface_manager_;
+  std::unique_ptr<exo::WMHelper> wm_helper_;
   std::unique_ptr<exo::Display> display_;
   std::unique_ptr<exo::wayland::Server> wayland_server_;
   class WaylandWatcher;