[Blink/Paint] Should not apply compositing recorder to scrolling layers

Any stacking context effects should have been applied by layers at a
higher hierarchy already. Applying the additional compositing recorder
will clip descendants inadvertently.

BUG=798148

Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I4eddaf12baa61f48e38b01fa4c15097a8765a9d3
Reviewed-on: https://chromium-review.googlesource.com/868740
Commit-Queue: Tien-Ren Chen <trchen@chromium.org>
Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#531123}
3 files changed