- Adds a histogram to measure time between streaming start and
  deserialization finished.

Bug: chromium:719172
Change-Id: Ib4ce24bee05a0db7e1bbf50d3bf456af89dbd2a6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1754721Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63252}