Make event-targeting asynchronous in window server.

services/ui/ws/window_server.cc

Index: services/ui/ws/window_server.cc
diff --git a/services/ui/ws/window_server.cc b/services/ui/ws/window_server.cc
index 3a46d4db3178b08b44c7b33ad70d372c6f0da0c3..9920972887ec796d8c13d06f5826151fe1c73d32 100644
--- a/services/ui/ws/window_server.cc
+++ b/services/ui/ws/window_server.cc
@@ -598,9 +598,8 @@ void WindowServer::UpdateNativeCursorFromMouseLocation(ServerWindow* window) {
   if (display_root) {
     EventDispatcher* event_dispatcher =
         display_root->window_manager_state()->event_dispatcher();
-    event_dispatcher->UpdateCursorProviderByLastKnownLocation();
-    display_root->display()->UpdateNativeCursor(
-        event_dispatcher->GetCurrentMouseCursor());
+    event_dispatcher->UpdateCursorProviderByLastKnownLocation(base::Bind(
+        &WindowServer::OnCursorUpdated, base::Unretained(this), display_root));
   }
 }
 
@@ -615,9 +614,15 @@ void WindowServer::UpdateNativeCursorIfOver(ServerWindow* window) {
   if (window != event_dispatcher->GetWindowForMouseCursor())
     return;
 
-  event_dispatcher->UpdateNonClientAreaForCurrentWindow();
+  event_dispatcher->UpdateNonClientAreaForCurrentWindow(base::Bind(
+      &WindowServer::OnCursorUpdated, base::Unretained(this), display_root));
+}
+
+void WindowServer::OnCursorUpdated(WindowManagerDisplayRoot* display_root) {
   display_root->display()->UpdateNativeCursor(
-      event_dispatcher->GetCurrentMouseCursor());
+      display_root->window_manager_state()
+          ->event_dispatcher()
+          ->GetCurrentMouseCursor());
 }
 
 bool WindowServer::IsUserInHighContrastMode(const UserId& user) const {