GitLab

In Pre-LayoutNG, selections are painted by LayoutText and LayoutReplaced.
We record SelectionVisualRect in LayoutObject::FragmentData, and check
for change of selection (in style and geometry) in
ObjectPaintInvalidator::InvalidateSelection, update SelectionVisualRect
and add needed invalidation rects into PartialInvalidationVisualRect.

In LayoutNG, selections are mainly painted by NGPaintFragment. Now we
keep track of NGPaintFragment's selection using
NGPaintFragment::SelectionVisualRect, and invlaidate the NGPaintFragment
if SelectionVisualRect changes.

PaintInvalidationReason::kSelection is treated as a full invalidation
reason for LayoutNG to simplify the logic (otherwise we need to support
partial raster invalidation in NGPaintFragment which seems not worth it,
with increased memory usage). This can be adjusted by the fact that we
now have finer grain selection invalidation in LayoutNG
(per NGPaintFragment) than Pre-LayoutNG (per LayoutObject).

For selection style changes (::selection pseudo style), we simply
invalidate the whole containing LayoutObject as the case is rare.

Bug: 849112
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_layout_ng;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I7a04a12e8007fb4c2841e5db9b17f37b6d9e2580
Reviewed-on: https://chromium-review.googlesource.com/1084314
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#564717}