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Fix border, background, and mask painting for inline blocks spanning two
or more lines or that are otherwise fragmented across multiple entities.

This involved refactoring the existing inline box painting code to allow
code sharing between legacy and LayoutNG painting code. It also required
changing LayoutNG painting to further distinguish between inline and non
inline boxes as the background image painting code in particular require
taking the other fragments for a fragmented object into account when the
image offsets and clipping is computed.

Finally, this cleans up the flow box paint logic for both legacy and NG.

This reverts r561186 (01dda95e) which in
turn was a revert of the original patch (r558871) which was reverted due
to a performance regression in blink_perf.paint color-changes benchmark.

To avoid the regression this patch moves construction of the box painter
from the inline box painter constructor to the paint methods where it is
needed, thereby avoiding the construction overhead in cases where cached
drawings may be reused. It also limits the lifecycle of the box painter.

Bug: 714962, 844624
Test: fast/backgrounds/border-radius-split-background-image.html

Cq-Include-Trybots: 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: I87ae744fdd204133e40b50721eca6947c81da817
Reviewed-on: https://chromium-review.googlesource.com/1144216
Commit-Queue: Emil A Eklund <eae@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577385}