Invalidate the bigger rect if one rect contains the other in LayoutObject::fullyInvalidateRect()

This reduces the cost along the path from
LayoutObject::invalidatePaintUsingContainer() to
RecordingSource::SetNeedsDisplayRect(), and the cost of
InvalidationRegion::Union().

BUG=602068

Review URL: https://codereview.chromium.org/1882473002

Cr-Commit-Position: refs/heads/master@{#386782}
2 files changed