GitLab

The layout test crash because:

1. We always create scrollbar layers even the outer viewport does not scrollable
2. Outer viewport does not scrollable then we don't create scroll node in
   NeedsScrollNode.
3. cc gen property trees alway create scroll node because it is scrollable in
   cc side (RequiresCompositingForRootScroller).

In this patch, we always add scroll node for layout view. After this CL, some
tests in virtual/android/fullscreen still failure but not crash, devtools mobile
emulator still other crash.

Bug: 865560
Cq-Include-Trybots: luci.chromium.try:linux-blink-gen-property-trees;luci.chromium.try:linux_layout_tests_layout_ng;luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I21a54cf7739055832b4634e28b850bf63543d9ed
Reviewed-on: https://chromium-review.googlesource.com/1156002
Commit-Queue: Jianpeng Chao <chaopeng@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584169}