mus: Implement ScreenMus::GetCursorScreenPoint().

components/mus/ws/window_tree.cc

Index: components/mus/ws/window_tree.cc
diff --git a/components/mus/ws/window_tree.cc b/components/mus/ws/window_tree.cc
index 0114bf5e89484c2ea0a5aa308e023c9861395187..14e6a6e7895fb81f6a350a09f23a2a83e657ef18 100644
--- a/components/mus/ws/window_tree.cc
+++ b/components/mus/ws/window_tree.cc
@@ -21,6 +21,7 @@
 #include "components/mus/ws/platform_display.h"
 #include "components/mus/ws/server_window.h"
 #include "components/mus/ws/server_window_observer.h"
+#include "components/mus/ws/user_display_manager.h"
 #include "components/mus/ws/window_manager_state.h"
 #include "components/mus/ws/window_server.h"
 #include "components/mus/ws/window_tree_binding.h"
@@ -1331,6 +1332,13 @@ void WindowTree::GetWindowManagerClient(
           this, std::move(internal)));
 }
 
+void WindowTree::GetCursorLocationMemory(
+    const GetCursorLocationMemoryCallback& callback) {
+  callback.Run(
+      window_server_->display_manager()->GetUserDisplayManager(user_id_)->
+      GetCursorLocationMemory());
+}
+
 void WindowTree::AddAccelerator(uint32_t id,
                                 mojom::EventMatcherPtr event_matcher,
                                 const AddAcceleratorCallback& callback) {