shell: Update focused surface pointer coordinates in popup grab

The commit 'input: Send leave and enter pair when the surface moves
under the cursor' introduced focused surface local pointer coordinates
to keep track of if a surface had been moved or transformed in a way
that the pointer posititon relative to that surface would change.
Update these coordinates also for the popup grab as otherwise every
pointer motion during a popup grab results in leave and then enter
events.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
Tested-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
diff --git a/desktop-shell/shell.c b/desktop-shell/shell.c
index d756076..ec72287 100644
--- a/desktop-shell/shell.c
+++ b/desktop-shell/shell.c
@@ -2982,6 +2982,11 @@
 	struct wl_resource *resource;
 	wl_fixed_t sx, sy;
 
+	if (pointer->focus) {
+		weston_view_from_global_fixed(pointer->focus, x, y,
+					      &pointer->sx, &pointer->sy);
+	}
+
 	weston_pointer_move(pointer, x, y);
 
 	wl_resource_for_each(resource, &pointer->focus_resource_list) {