ozone/wayland: Clean up WaylandCursor

This CL makes a code cleanup in WaylandCursor class:
 - Remove unneeded/unused header includes
 - Switch to forward declarations instead of header includes
 where possible
 - Fix lint errors

Bug: 578890
Change-Id: I481723749b1c7ddb5dcd7d4569d3517be8a924ec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1525104
Reviewed-by: Maksim Sisov <msisov@igalia.com>
Commit-Queue: Nick Yamane <nickdiego@igalia.com>
Cr-Commit-Position: refs/heads/master@{#641452}
2 files changed