Use ui::Event instead of mojom::EventPtr in mash/wm.

mash/wm/root_window_controller.h

Index: mash/wm/root_window_controller.h
diff --git a/mash/wm/root_window_controller.h b/mash/wm/root_window_controller.h
index 5635d4427a112b4f3febedd745d362541d6510d3..c64eb31cc93bbc3902cbf2fa7e64159a2fc348d9 100644
--- a/mash/wm/root_window_controller.h
+++ b/mash/wm/root_window_controller.h
@@ -20,6 +20,10 @@ namespace mus {
 class WindowManagerClient;
 }
 
+namespace ui {
+class Event;
+}
+
 namespace mash {
 namespace wm {
 
@@ -58,7 +62,7 @@ class RootWindowController : public mus::WindowObserver,
 
   mus::WindowManagerClient* window_manager_client();
 
-  void OnAccelerator(uint32_t id, mus::mojom::EventPtr event);
+  void OnAccelerator(uint32_t id, const ui::Event& event);
 
  private:
   explicit RootWindowController(WindowManagerApplication* app);