Make event-targeting asynchronous in window server.

services/ui/ws/window_server.h

Index: services/ui/ws/window_server.h
diff --git a/services/ui/ws/window_server.h b/services/ui/ws/window_server.h
index f79cf963966e600304070af38dffa3e166c6339e..e2e60f58250a5d63206070ee604212fbd2b97432 100644
--- a/services/ui/ws/window_server.h
+++ b/services/ui/ws/window_server.h
@@ -13,6 +13,7 @@
 #include <vector>
 
 #include "base/macros.h"
+#include "base/memory/weak_ptr.h"
 #include "base/optional.h"
 #include "cc/ipc/frame_sink_manager.mojom.h"
 #include "mojo/public/cpp/bindings/binding.h"
@@ -37,6 +38,7 @@ class DisplayManager;
 class GpuHost;
 class ServerWindow;
 class UserActivityMonitor;
+class WindowManagerDisplayRoot;
 class WindowManagerState;
 class WindowServerDelegate;
 class WindowTree;
@@ -283,6 +285,8 @@ class WindowServer : public ServerWindowDelegate,
   // |window|.
   void UpdateNativeCursorIfOver(ServerWindow* window);
 
+  void OnCursorUpdated(WindowManagerDisplayRoot* display_root);
+
   bool IsUserInHighContrastMode(const UserId& user) const;
 
   // Finds the parent client that will embed |surface_id| and claims ownership
@@ -388,6 +392,8 @@ class WindowServer : public ServerWindowDelegate,
       frame_sink_manager_client_binding_;
   cc::mojom::FrameSinkManagerPtr frame_sink_manager_;
 
+  base::WeakPtrFactory<WindowServer> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(WindowServer);
 };