All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=817942

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=d5d53a5a0fa7bbc2e48ca9dad2b6e00ef6f61f6f5f4d9c61c0e9297bef7ef796


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

android-webview-nexus6

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/14e5ac24440000

😿 Pinpoint job stopped with an error.
https://pinpoint-dot-chromeperf.appspot.com/job/14e5ac24440000

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/117f26de440000

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/16b45bde440000

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/1782a3ee440000

Kicking off a few more bisects.

📍 Found a significant difference after 1 commit.
https://pinpoint-dot-chromeperf.appspot.com/job/16b45bde440000

Enable Delta Anti-Aliasing and Rebaseline by liyuqian@google.com
https://chromium.googlesource.com/chromium/src/+/e3053cdf8cfac55d0a4589a7f1fcc60796d60c41

Understanding performance regressions:
  http://g.co/ChromePerformanceRegressions

📍 Found a significant difference after 1 commit.
https://pinpoint-dot-chromeperf.appspot.com/job/117f26de440000

Enable Delta Anti-Aliasing and Rebaseline by liyuqian@google.com
https://chromium.googlesource.com/chromium/src/+/e3053cdf8cfac55d0a4589a7f1fcc60796d60c41

Understanding performance regressions:
  http://g.co/ChromePerformanceRegressions

📍 Found a significant difference after 1 commit.
https://pinpoint-dot-chromeperf.appspot.com/job/1782a3ee440000

Enable Delta Anti-Aliasing and Rebaseline by liyuqian@google.com
https://chromium.googlesource.com/chromium/src/+/e3053cdf8cfac55d0a4589a7f1fcc60796d60c41

Understanding performance regressions:
  http://g.co/ChromePerformanceRegressions

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/12a56b45440000

📍 Couldn't reproduce a difference.
https://pinpoint-dot-chromeperf.appspot.com/job/12a56b45440000

The following revision refers to this bug:
  https://skia.googlesource.com/skia/+/ab46ac5ee801a048552425274804309eaaf9a805

commit ab46ac5ee801a048552425274804309eaaf9a805
Author: Yuqian Li <liyuqian@google.com>
Date: Thu Mar 22 16:24:24 2018

Better decisions about choosing AAA versus DAA

The Chrome perf regressions (817942, 819185) are
caused by the bad choices to use DAA instead of
AAA for stroking simple curves. (BTW, in my tests,
DAA is still faster than SAA so it's not too much
of a regression.)

We previously only considered the number of line segments,
but not the length of each segment. That leads to our
wrong judgement of the path complexity (the number of
intersections per scan line) when there are many short
line segments.

The change will bring the following performance change
to our nanobench:

    8.45% slower in clip_strategy_path_10
    8.39% slower in draw_stroke_bezier_quad_square_bevel_10
    3.91% slower in chart_aa
    3.76% faster in lines
    6.29% faster in path_stroke_big_oval
   22.81% faster in path_stroke_big_circle
   24.44% faster in giantdashline_vert_2

The two slower cases, clip_strategy_path_10
and draw_stroke_bezier_quad_square_bevel_10 are caused by
choosing AAA over DAA. Those two tests do seem to be simple
strokes. I'll later investigate why AAA is slower than DAA
for those two cases.

For now, I think that this change is sufficient to address
those chromium perf regresssions.

Bug:  chromium:817942   chromium:819185 
Change-Id: I1d13c968b17f257b4ede4c70e552db5016baf1ab
Reviewed-on: https://skia-review.googlesource.com/115583
Commit-Queue: Yuqian Li <liyuqian@google.com>
Reviewed-by: Cary Clark <caryclark@google.com>

[modify] https://crrev.com/ab46ac5ee801a048552425274804309eaaf9a805/src/core/SkScan_AntiPath.cpp

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/011343525c605af1203468a807d5286ffca19a27

commit 011343525c605af1203468a807d5286ffca19a27
Author: skia-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com <skia-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Date: Thu Mar 22 20:30:28 2018

Roll src/third_party/skia/ 5fba7ad39..1b6930f55 (9 commits)

https://skia.googlesource.com/skia.git/+log/5fba7ad39a96..1b6930f55c7c

$ git log 5fba7ad39..1b6930f55 --date=short --no-merges --format='%ad %ae %s'
2018-03-22 angle-skia-autoroll Roll skia/third_party/externals/angle2/ 8b92c53b8..107c72476 (2 commits)
2018-03-22 mtklein lock before using fCacheKeys in ~SkImageFilter()
2018-03-22 halcanary dm: fix unused-private-field error when skia_use_expat=false
2018-03-22 mtklein add repro case for skia:7674
2018-03-22 mtklein rm SkTDArray::{Deleter,release()}
2018-03-22 fmalita [sksg] Simplify TrimEffect
2018-03-22 herb Remove the last uses of auto glyph cache.
2018-03-21 liyuqian Better decisions about choosing AAA versus DAA
2018-03-22 liyuqian Reland "Remove legacy precision boundary"

Created with:
  roll-dep src/third_party/skia
BUG= chromium:817942   chromium:819185 


The AutoRoll server is located here: https://autoroll.skia.org

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.


CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel;luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
TBR=jvanverth@chromium.org

Change-Id: Ica709d14fc6aa380c5facf6ca2f30c31e92f2388
Reviewed-on: https://chromium-review.googlesource.com/976382
Reviewed-by: skia-chromium-autoroll <skia-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Commit-Queue: skia-chromium-autoroll <skia-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#545231}
[modify] https://crrev.com/011343525c605af1203468a807d5286ffca19a27/DEPS

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/11bccfe5440000

📍 Found a significant difference after 1 commit.
https://pinpoint-dot-chromeperf.appspot.com/job/11bccfe5440000

Remove SK_SUPPORT_LEGACY_AA_CHOICE by liyuqian@chromium.org
https://chromium-review.googlesource.com/c/chromium/src/+/976622/1

Understanding performance regressions:
  http://g.co/ChromePerformanceRegressions

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/14ffeb93440000

📍 Found a significant difference after 1 commit.
https://pinpoint-dot-chromeperf.appspot.com/job/14ffeb93440000

Remove SK_SUPPORT_LEGACY_AA_CHOICE by liyuqian@chromium.org
https://chromium-review.googlesource.com/c/chromium/src/+/976622/1

Understanding performance regressions:
  http://g.co/ChromePerformanceRegressions

 Issue 830779  has been merged into this issue.