The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/67549b5d7c4973d062669bfca74e5c5af074c476

commit 67549b5d7c4973d062669bfca74e5c5af074c476
Author: Wez <wez@chromium.org>
Date: Wed Nov 07 21:07:24 2018

Allow runner scripts to fall-back to emulated CPU.

- Refactor the QemuTarget selection of CPU to emulate, to allow it to
  run x64 under software emulated CPU.
- Enable software-emulated-CPU fall-back by default, if /dev/kvm is not
  accessible for reading & writing.
- Add a require_kvm parameter to QemuTarget, and wire it to a common
  --qemu-require-kvm command-line argument.
- Add --qemu-require-kvm to the Fuchsia x64 builders, to ensure that we
  spot any regressions that break KVM on the bots.

Bug:  902607 
Change-Id: I60f69b7cb7f5458ccf4a0a2d932235d823b6f932
Reviewed-on: https://chromium-review.googlesource.com/c/1318832
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606157}
[modify] https://crrev.com/67549b5d7c4973d062669bfca74e5c5af074c476/build/fuchsia/common_args.py
[modify] https://crrev.com/67549b5d7c4973d062669bfca74e5c5af074c476/build/fuchsia/qemu_target.py
[modify] https://crrev.com/67549b5d7c4973d062669bfca74e5c5af074c476/testing/buildbot/chromium.linux.json
[modify] https://crrev.com/67549b5d7c4973d062669bfca74e5c5af074c476/testing/buildbot/waterfalls.pyl
[modify] https://crrev.com/67549b5d7c4973d062669bfca74e5c5af074c476/third_party/blink/tools/blinkpy/web_tests/port/fuchsia.py