To measure the performance of a binary I can do two different things:
- StartMeasuring
- RunBinary --times=1000
- StopMeasuring
The delay between start/stop of measurement and start/stop of running the binary might cause a bit of flakiness, but it should be ok I think.

- RunBinary --times=1000
- StartMeasuring
- StopMeasuring
- Wait for binary to stop
This is the current approach. The time it takes to run the binary is variable, so it's difficult to time this right. I could fix this by letting the binary run indefinitely and using 'kill binary' at the end. It would require adding a RunAsync function next to the Run function.

Another note:
We're decoding as fast as possible, and we want the CPU usage to be as low as possible. But this might not always be correct. If we have the perfect HW decoder, the CPU usage would actually go up to a 100%, as the CPU would become the bottleneck.

Measuring CPU usage would only make sense if we throttle the number of JPEG decodes, or if we compare the total runtime between software and hardware decoding.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e61473d95efa8f75bcbb17fd116c31c26355f6ac

commit e61473d95efa8f75bcbb17fd116c31c26355f6ac
Author: David Staessens <dstaessens@chromium.org>
Date: Thu Dec 13 01:03:13 2018

media/gpu/test: Allow file paths in jpeg decode accelerator unittest.

This CL removes a check from the jpeg decode accelerator unittest, that makes
the test fail if the "--jpeg_filenames" parameter contains a path rather than a
filename. This functionality is required when running tests from Tast.

e.g.: ./jpeg_decode_accelerator_unittest
--jpeg_filenames=/usr/local/share/tast/peach_pi-1280x720.jpg

TEST=JPEG decode accelerator unittest on nocturne

BUG=912413

Change-Id: I96e6f05148ad6bd0d623936f6c1ca3c626250dd3
Reviewed-on: https://chromium-review.googlesource.com/c/1369756
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Commit-Queue: David Staessens <dstaessens@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616133}
[modify] https://crrev.com/e61473d95efa8f75bcbb17fd116c31c26355f6ac/media/gpu/jpeg_decode_accelerator_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/tast-tests/+/e083cf9b2207d1bc6dee1b4128cbe3aee326665b

commit e083cf9b2207d1bc6dee1b4128cbe3aee326665b
Author: David Staessens <dstaessens@chromium.org>
Date: Fri Dec 14 03:28:14 2018

video.DecodeAccelJPEGPerf: Add functionality to disable CPU frequency scaling.

This functionality is required by the JPEG HW decode accelerator performance
test that is currently being migrated to Tast.

Also adds a bit more documentation to the cpu.MeasureUsage function.

TEST=DecodeAccelJPEGPerf on nocturne
BUG=chromium:912413
Change-Id: Iac97d92073a6b229fb5cd4224b7df4b8c9c82514
Reviewed-on: https://chromium-review.googlesource.com/1364591
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: David Staessens <dstaessens@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>

[modify] https://crrev.com/e083cf9b2207d1bc6dee1b4128cbe3aee326665b/src/chromiumos/tast/local/bundles/cros/video/lib/cpu/cpu.go

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/tast-tests/+/83336a7c6b4c1f1afae6f0d72218b22177ba378f

commit 83336a7c6b4c1f1afae6f0d72218b22177ba378f
Author: David Staessens <dstaessens@chromium.org>
Date: Sat Dec 15 06:40:43 2018

video.DecodeAccelJPEGPerf: Add functionality to disable CPU thermal throttling.

This functionality is required by the JPEG HW decode accelerator performance
test that is currently being migrated to Tast.

TEST=DecodeAccelJPEGPerf on nocturne
CQ-DEPEND=CL:1364591
BUG=chromium:912413

Change-Id: I118f63c787eccfa66c448ac471941b9c77a889f0
Reviewed-on: https://chromium-review.googlesource.com/1364991
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: David Staessens <dstaessens@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>

[modify] https://crrev.com/83336a7c6b4c1f1afae6f0d72218b22177ba378f/src/chromiumos/tast/local/bundles/cros/video/lib/cpu/cpu.go

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/tast-tests/+/a8430f6e2edc5ad18499b64b0cc6ed6a0bad3475

commit a8430f6e2edc5ad18499b64b0cc6ed6a0bad3475
Author: David Staessens <dstaessens@chromium.org>
Date: Tue Dec 18 04:47:06 2018

video.DecodeAccelJPEGPerf: Migrate DecodeAccelJPEGPerf test to Tast.

This test benchmarks JPEG SW/HW decode performance, and corresponds to the
video_JDAPerf test in autotest.

TEST=DecodeAccelJPEGPerf on nocturne
CQ-DEPEND=CL:1364991
BUG=chromium:912413

Change-Id: I6b2dfb8a8271bd111dd143685cea93dcc5f6c0c9
Reviewed-on: https://chromium-review.googlesource.com/1369986
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: David Staessens <dstaessens@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>

[modify] https://crrev.com/a8430f6e2edc5ad18499b64b0cc6ed6a0bad3475/src/chromiumos/tast/local/chrome/bintest/bintest.go
[add] https://crrev.com/a8430f6e2edc5ad18499b64b0cc6ed6a0bad3475/src/chromiumos/tast/local/bundles/cros/video/decode_accel_jpeg_perf.go
[modify] https://crrev.com/a8430f6e2edc5ad18499b64b0cc6ed6a0bad3475/src/chromiumos/tast/local/bundles/cros/video/lib/cpu/cpu.go