Add bounds check to TrailingArray. This appears to be perf neutral on the benchmarks we track.
Pull request: https://github.com/WebKit/WebKit/pull/29240
Committed 279460@main (bd841a095367): <https://commits.webkit.org/279460@main> Reviewed commits have been landed. Closing PR #29240 and removing active labels.
<rdar://problem/128961374>