Add a new flag to assist in landing optimization update.
Add a new flag to assist in landing optimization update.

This is as described in the new comment to assist in updating V8 so https://codereview.chromium.org/1324623005/ can be landed.

TBR=dpranke

Review URL: https://codereview.chromium.org/1330423002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#348193}

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