[SPv175] Use kSrcOver to paint inline mask

Previously we may used kDstIn which composited the mask painting
directly with the masked contents. However, for SPv175 we'll issue
the compositing op in PaintChunkToCcLayer so we should use kDstIn
during painting.

Bug: 771643
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I526fd06425d545a526f0a8413e74712ee1f4647f
Reviewed-on: https://chromium-review.googlesource.com/882302
Reviewed-by: Tien-Ren Chen <trchen@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#531438}
6 files changed