"In short, autoninja is preferable because it'll detect whether or not goma is enabled and set the right -j/-l flags correctly." from https://chromium-review.googlesource.com/c/chromium/src/+/986872#message-0aaaa967c266ab240712cb0dcd70f22d9a199a97

The following revision refers to this bug:
  https://chrome-internal.googlesource.com/chrome/tools/code-coverage/+/79d1720277b9fd1b04c082a8ccc192b520112054

commit 79d1720277b9fd1b04c082a8ccc192b520112054
Author: Max Moroz <mmoroz@google.com>
Date: Thu Jan 03 17:55:04 2019

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/06576294dffd45fa06e32afaf89fd7b59fa51c57

commit 06576294dffd45fa06e32afaf89fd7b59fa51c57
Author: Max Moroz <mmoroz@chromium.org>
Date: Thu Jan 03 19:22:52 2019

Coverage script: use autoninja instead of ninja and custom goma checker.

TEST=tools/code_coverage/coverage_test.py

Bug:  869451 
Change-Id: I29423a45d6542e358e7157bc6af7f9208969a436
Reviewed-on: https://chromium-review.googlesource.com/c/1394594
Commit-Queue: Max Moroz <mmoroz@chromium.org>
Reviewed-by: Yuke Liao <liaoyuke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619714}
[modify] https://crrev.com/06576294dffd45fa06e32afaf89fd7b59fa51c57/tools/code_coverage/coverage.py