Tracing block coverage prints raw generated slots in the format:
{start_source_position,end_source_position}

Slots are printed before being mutated during coverage collection.

Bug: v8:6000
Change-Id: I3423e226a124e00c6b13ccd8dddb13d00e4989c7
Reviewed-on: https://chromium-review.googlesource.com/579374Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46807}