Reserve HashMap capacity in InlineDisplayContentBuilder::computeIsFirstIsLastBoxForInlineContent() since we know approximately how many items we'll add.
<rdar://problem/105697311>
Pull request: https://github.com/WebKit/WebKit/pull/10400
Committed 260579@main (eeae2b39ab0c): <https://commits.webkit.org/260579@main> Reviewed commits have been landed. Closing PR #10400 and removing active labels.