All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=776960

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=2ba4a5f900eb345a58edcd315fa3d7f9e3c41fbf44f11bff330cc169032b9c51


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

android-webview-nexus6

Started bisect job https://chromeperf.appspot.com/buildbucket_job_status/8965180713798035952

Khushal found it. (Thank you)

It turns out this is fine and expected.
Certain things can cause a veto of checker-images. This would force the image decoding to be synchronous and thus impact Blink's FPS.

One of the test cases changes the src[1], which results in using synchronous decoding.

[1] https://cs.chromium.org/chromium/src/tools/perf/page_sets/image_decoding_cases/yuv_decoding.html

So when we correctly included vetoes, we expected a regression in the vetoed cases.

=== BISECT JOB RESULTS ===
Perf regression found with culprit

Suspected Commit
  Author : Vladimir Levin
  Commit : 9167e1c4eb3a1b6d094399e35efe427185303428
  Date   : Wed Oct 18 21:28:24 2017
  Subject: cc: Plumb decoding mode state to checker image tracker.

Bisect Details
  Configuration: android_webview_nexus6_aosp_perf_bisect
  Benchmark    : smoothness.image_decoding_cases
  Metric       : mean_frame_time/mean_frame_time
  Change       : 57.41% | 19.12 -> 30.0973333333

Revision             Result                   N
chromium@509828      19.12 +- 3.6661          6      good
chromium@509863      18.5375 +- 0.579391      6      good
chromium@509872      18.434 +- 0.621802       6      good
chromium@509876      18.548 +- 0.596361       6      good
chromium@509878      18.4893 +- 0.455512      6      good
chromium@509879      31.5325 +- 0.44701       6      bad       <--
chromium@509880      31.5537 +- 0.37241       6      bad
chromium@509897      30.0973 +- 0.604906      6      bad

To Run This Test
  src/tools/perf/run_benchmark -v --browser=android-webview --output-format=chartjson --upload-results --pageset-repeat=1 --also-run-disabled-tests smoothness.image_decoding_cases

More information on addressing performance regressions:
  http://g.co/ChromePerformanceRegressions

Debug information about this bisect:
  https://chromeperf.appspot.com/buildbucket_job_status/8965180713798035952


For feedback, file a bug with component Speed>Bisection