service worker: Remove histogram ServiceWorker.StartNewWorker.Status.

The data was dominated by the case where startup was aborted due to the
update check resulting in no byte-for-byte change found.  We were not
consistent in whether to log that as EXISTS or ABORT. Furthermore, there
is work to move the update check to the browser so starting the worker
won't happen until after a byte-for-byte change is found, which will
completely change the data.

Bug: 972784
Change-Id: I730ce9f6ddfb140adc9d220225b639503e6febdf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1660297
Reviewed-by: Makoto Shimazu <shimazu@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Auto-Submit: Matt Falkenhagen <falken@chromium.org>
Commit-Queue: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#669762}
4 files changed