Prior to this CL, and after [1], the mask_type() field of the
PictureLayer created by UpdateMaskLayer was not properly set. This
meant that for large masks, the standard tiling logic kicked in and
tiled the mask, which (after [1]) was not supported and resulted in
a DCHECK and/or the mask not properly being applied. This fixes that
bug. I also added a backdrop-filter/mask test with a large mask
to ensure this works.

[1] https://chromium.googlesource.com/chromium/src/+/310cae44aff889a75fc85ce5ec89d9341eccc665

Bug: 992782
Change-Id: Ibc461638abdeedd8ff9f4730a1e81f6442400bd8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1764679
Commit-Queue: Mason Freed <masonfreed@chromium.org>
Auto-Submit: Mason Freed <masonfreed@chromium.org>
Reviewed-by: enne <enne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#689978}