[AssistData] Prevent early delete on Android if a11y is running

This CL addresses a corner-case when the full accessibility engine
could be running at the end of a snapshot, in which case we do not
want to tear down the C++ objects.

AX-Relnotes: N/A
Bug: 346367351
Change-Id: I10665b9057e90465533227d192f3274ea01c5bec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5616755


Reviewed-by: Abigail Klein <abigailbklein@google.com>
Commit-Queue: Mark Schillaci <mschillaci@google.com>
Auto-Submit: Mark Schillaci <mschillaci@google.com>
Commit-Queue: Abigail Klein <abigailbklein@google.com>
Cr-Commit-Position: refs/heads/main@{#1312993}