With BytecodeArray flushing the SFI->BytecodeArray pointer will become pseudo weak.
In order to prevent instrumented bytecode from being flushed while the function is
being debugged, hold onto the instrumented bytecode strongly.

BUG=v8:8395

Change-Id: Ie346732b77833afa0595a84a4956295e50855392
Reviewed-on: https://chromium-review.googlesource.com/c/1312849Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57569}