Fix short-circuit logic in HitTester
Fix short-circuit logic in HitTester

|= (the bitwise or-assignement operator) does not do short-circuiting.
It isn't an error to call is_point_clipped_in_for_clip_chain again in
this case, but it has the potential to do a lot of extra work.

servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender