All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=617461

Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?keys=agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICg3JTvsAoM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICgnKubtgoM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICg3KbCsAoM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICgnKuNpwoM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICgnM3ZpgoM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICgnLeOswoM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICg3N7NpwoM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICgnPmGswoM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICg3MjVvQoM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICg3PDrugoM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICgnMvjrQoM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICg3KTfpAoM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICgnMuFtAkM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICgnI3GpAoM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICgnNnNrwoM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICg3MaQswoM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICgnI3cuQoM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICgnI2oqAoM


Bot(s) for this bug's original alert(s):

android-galaxy-s5
android-nexus5
android-nexus5X
android-one

=== Auto-CCing suspected CL author alancutter@chromium.org ===

Hi alancutter@chromium.org, the bisect results pointed to your CL below as possibly
causing a regression. Please have a look at this info and see whether
your CL be related.


===== BISECT JOB RESULTS =====
Status: completed


===== SUSPECTED CL(s) =====
Subject : Allow transitions on background-size with positionally matched keywords
Author  : alancutter
Commit description:
  
This change allows CSS transitions to interpolate between lists with
matching keywords.
This affects interpolation for the following properties:
 - border-image-width
   This property is not animatable according to spec:
   https://drafts.csswg.org/css-backgrounds-3/#the-border-image-width

 - background-size
   Values are now interpolable if their keywords are positionally matched:
   https://github.com/w3c/csswg-drafts/commit/a5f9de921fa7834c79ee15660d9d86528bce1607

 - -webkit-background-size
 - -webkit-mask-size
   These mirror the animation behaviour of background-size.

This change only affects CSS Transitions for the sake of a small mergable patch.
CSS Animations behaviour will be brought in line in a separate patch.

This change ensures we have compatible behaviour with other browsers for
transitioning between single length background-size values e.g.
"background-size: 50%" to "background-size: 100%"

BUG= 616072 

Review-Url: https://codereview.chromium.org/2027933002
Cr-Commit-Position: refs/heads/master@{#397661}
Commit  : 8793a7bac4d2d56e38c8bd406920128e1ceb7a9a
Date    : Fri Jun 03 08:14:27 2016


===== TESTED REVISIONS =====
Revision         Mean     Std Dev    N  Good?
chromium@397652  1.43893  0.149368   6  good
chromium@397660  1.5426   0.149318   5  good
chromium@397661  2.15386  0.110613   5  bad    <--
chromium@397662  2.12315  0.0590615  5  bad
chromium@397664  2.14884  0.167597   5  bad
chromium@397668  2.26618  0.122451   5  bad

Bisect job ran on: android_nexus5_perf_bisect
Bug ID: 617461

Test Command: src/tools/perf/run_benchmark -v --browser=android-chromium --output-format=chartjson --upload-results --also-run-disabled-tests thread_times.key_silk_cases
Test Metric: thread_raster_cpu_time_per_frame/thread_raster_cpu_time_per_frame
Relative Change: 55.96%
Score: 99.9

Buildbot stdio: http://build.chromium.org/p/tryserver.chromium.perf/builders/android_nexus5_perf_bisect/builds/3719
Job details: https://chromeperf.appspot.com/buildbucket_job_status/9010664843128041888


Not what you expected? We'll investigate and get back to you!
  https://chromeperf.appspot.com/bad_bisect?try_job_id=5789887765151744

| O O | Visit http://www.chromium.org/developers/speed-infra/perf-bug-faq
|  X  | for more information addressing perf regression bugs. For feedback,
| / \ | file a bug with component Tests>AutoBisect.  Thank you!

After my change the CPU usage graph jumps up by ~1ms. Earlier in the graph there was an approximately equal 1ms drop in CPU usage.

The progression range for the drop is ttps://chromium.googlesource.com/chromium/src/+log/45cf0b58103c62895d4e4c8223e798bf84a42345..563b5b2ddbe47b5ad008c805a40853e97233f3b6, the most likely candidate would have been 4d344058522e01d85162fcd1a9e5f4b747db9383 (Handling transition animation between non-interpolable values).

That change more cases stop animating than intended ( crbug.com/616072 ), my change 8793a7bac4d2d56e38c8bd406920128e1ceb7a9a (Allow transitions on background-size with positionally matched keywords) re-enables some of those animations and subsequently reverts the performance gains we got from not running them.

Working as intended. Glad to see our perf tooling is catching these changes.