[blink-gen-property-trees] Add effect node for overlay scrollbar

This issue is caused by:
1. scrollbar layer linked to the page's effect node
2. change scrollbar opacity actually change the opacity in effect node

In this patch, we create effect node when walk thought layout object
with overlay scrollbars (PaintedOverlayScrollbarLayer for Aura and
SolidColorScrollbarLayer for Android).

Bug: 846790
Cq-Include-Trybots: luci.chromium.try:linux-blink-gen-property-trees;luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Id4d53154324d142228f46ad308bd2f4ccdcf3153
Reviewed-on: https://chromium-review.googlesource.com/1114127
Reviewed-by: Philip Rogers <pdr@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Commit-Queue: Jianpeng Chao <chaopeng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573173}
18 files changed