Visualizes --trace-gc-object-stats output.

No-try: true
Bug: v8:7266
Change-Id: I5beb15d63e645484f07fe5f2341105c4cfe0b550
Reviewed-on: https://chromium-review.googlesource.com/860580
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50587}