While testing the perf for v8-etw, I noticed that the runtime flag
didn't completely guard from event emission. This change fixes that.

Bug: v8:11043
Change-Id: Iee919e6030214e18173c93e4426d6437aed08235
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2757894Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Sara Tang <sartang@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#73424}