Spot fix for crash.

Non-deterministic initialization order strikes again!

On some instances of Chrome, one of the startup critical notice systems
is not always fully initialized when the browser attempts to show
startup promos. In User Education 2.5, a precondition checks the state
of the critical notices, which - if this ordering holds - can crash.

For now, we have a workaround where we delay startup promos one frame.
This should fix the crash, and will need to be merged to beta as well.

A more thorough safeguard will be put in in a follow-up patch that will
be ToT-only.

Bug: 439739546
Change-Id: I4f97b7304a274c69171443721481ed29f620a825
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6865451
Commit-Queue: Dana Fried <dfried@chromium.org>
Reviewed-by: Muhammad Salmaan <musalmaan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1503971}