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This patch rebaselines paint/invalidation failures that are
caused when empty |LayoutBlowFlow| becomes non-empty, or
vice-versa.

This is |NGPaintFragment|-specific behavior. When
|LayoutBlockFlow| got or lost |NGPaintFragment|, its
|DisplayItemClient| changes between |LayoutBlockFlow| and
corresponding |NGPaintFragment|.

|FragmentItem| does not have this behavior; i.e., uses
|LayoutBlockFlow| as |DisplayItemClient|, and that the
invalidation results are more similar to legacy.

TBR=wangxianzhu@chromium.org, yosin@chromium.org

Bug: 982194
Change-Id: Id433962da7a32e51ca6046135ccc3e300b3cb7b6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2096796Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#748899}