Keep root_location to be in pixels and display coordinates in WS.

services/ui/ws/display_manager.cc

Index: services/ui/ws/display_manager.cc
diff --git a/services/ui/ws/display_manager.cc b/services/ui/ws/display_manager.cc
index 6575884cac1209f67717c14e972e2202cd1eae76..9832ab16679f4f7a1d6d91c8dca13bbbaacf88ae 100644
--- a/services/ui/ws/display_manager.cc
+++ b/services/ui/ws/display_manager.cc
@@ -199,17 +199,22 @@ void DisplayManager::OnActiveUserIdChanged(const UserId& previously_active_id,
                                            const UserId& active_id) {
   WindowManagerState* previous_window_manager_state =
       window_server_->GetWindowManagerStateForUser(previously_active_id);
-  gfx::Point mouse_location_on_screen;
+  gfx::Point mouse_location_on_display;
+  int64_t mouse_display_id = 0;
   if (previous_window_manager_state) {
-    mouse_location_on_screen = previous_window_manager_state->event_dispatcher()
-                                   ->mouse_pointer_last_location();
+    mouse_location_on_display =
+        previous_window_manager_state->event_dispatcher()
+            ->mouse_pointer_last_location();
+    mouse_display_id = previous_window_manager_state->event_dispatcher()
+                           ->mouse_pointer_display_id();
     previous_window_manager_state->Deactivate();
   }
 
   WindowManagerState* current_window_manager_state =
       window_server_->GetWindowManagerStateForUser(active_id);
   if (current_window_manager_state)
-    current_window_manager_state->Activate(mouse_location_on_screen);
+    current_window_manager_state->Activate(mouse_location_on_display,
+                                           mouse_display_id);
 }
 
 void DisplayManager::OnDisplayAdded(const display::Display& display,