Reland Paint solid color backgrounds which are equivalent to locally attached into scrolling contents layer (patchset #9 id:160001 of https://codereview.chromium.org/2264663002/ )
If we have a solid color background whose bounds / visible rect is equivalent to the padding-box we can treat it as locally attached and paint it into the scrolling contents layer. This enables composited scrolling with sub-pixel text anti-aliasing.
TBR=chrishtr
BUG=381840
TEST=CompositedLayerMappingTest.ShouldPaintBackgroundOntoScrollingContentsLayer
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Review-Url: https://codereview.chromium.org/2302743004
Cr-Commit-Position: refs/heads/master@{#417858}
31 files changed
