Able to reproduce the issue on chrome reported version 68.0.3440.17 and on latest chrome 69.0.3455.0 using Mac 10.12.6 and Windows-10. As this issue is seen from M-60(60.0.3112.0), hence considering this issue a Non-Regression and marking it as Untriaged.
Note: Issue is not seen on Ubuntu 14.04.

Thanks!

Here's a minimalist demo. The issue seems to disappear when we constrain the numbers to integers or integers+0.5 (e.g. try changing the 499.9 to 500).

Deleted: index.html.zip 858 bytes

index.html.zip 858 bytes Download

senorblanco: more gpu path rasterization bugs for you to triage/investigate.

I was able to repro this one only after switching to the Intel GPU on my MBP. So likely --gpu-rasterization-msaa-sample-count=0 would be necessary to repro on the discrete GPU.

This one also seems to be GrAALinearizingConvexPathRenderer; possibly a dupe of  http://crbug.com/869172 .

Brian, could you take a look?

The following revision refers to this bug:
  https://skia.googlesource.com/skia/+/20ea47a5d9aa99b20a7745efce0f6c325666b463

commit 20ea47a5d9aa99b20a7745efce0f6c325666b463
Author: Brian Salomon <bsalomon@google.com>
Date: Wed Sep 05 19:20:49 2018

Fix missing triangle when miter point omitted in GrAAConvexTessellator.

This issue is seen in the existing GPU results for GM "strokes_round".

Detected while investigating the below bug. However, the real bug there
caused by bad tessellations appears to be coming from
GrAAConvexPathRenderer.

BUG= chromium:851637 

Change-Id: If4e653d10823d53f68bb9bf6bb77875cf391426f
Reviewed-on: https://skia-review.googlesource.com/151368
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>

[modify] https://crrev.com/20ea47a5d9aa99b20a7745efce0f6c325666b463/src/gpu/ops/GrAAConvexTessellator.cpp

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f65d3e611c4dce936326bf53b5a065babef1129b

commit f65d3e611c4dce936326bf53b5a065babef1129b
Author: skia-chromium-autoroll <skia-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Date: Wed Sep 05 23:51:31 2018

Roll src/third_party/skia 29a4a684af25..0c3dc59fc1c6 (14 commits)

https://skia.googlesource.com/skia.git/+log/29a4a684af25..0c3dc59fc1c6


git log 29a4a684af25..0c3dc59fc1c6 --date=short --no-merges --format='%ad %ae %s'
2018-09-05 swiftshader-skia-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com Roll third_party/externals/swiftshader fe5861bf5bb1..ad5c2952ca88 (5 commits)
2018-09-05 mtklein@google.com fix sw extended transfer functions
2018-09-05 mtklein@google.com fix typo
2018-09-05 mtklein@google.com add src/opts headers to .gni files
2018-09-05 bsalomon@google.com Don't use MEM_MOVE=true with SkTArrays of sk_sp
2018-09-05 jvanverth@google.com Rip out variable offsetting
2018-09-05 bsalomon@google.com Fix GrAAConvexTessellator to handle cases slightly concave bistectors.
2018-09-05 recipe-roller@chromium.org Roll recipe dependencies (trivial).
2018-09-05 herb@google.com Centralize the predicate for a glyph being too large for the atlas
2018-09-05 bsalomon@google.com Fix missing triangle when miter point omitted in GrAAConvexTessellator.
2018-09-05 brianosman@google.com Remove SK_USE_LEGACY_PRIMARIES_TO_XYZ
2018-09-05 skcms-skia-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com Roll skia/third_party/skcms 8a251fa55434..da4870efd7b7 (1 commits)
2018-09-05 caryclark@google.com Revert "makeSurface defaults to raster"
2018-09-05 egdaniel@google.com On GrAHardwareBufferImageGenerator store the owned texture as a GrGpuResource instead of GrTexture.


Created with:
  gclient setdep -r src/third_party/skia@0c3dc59fc1c6

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

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;luci.chromium.try:win_optional_gpu_tests_rel

BUG= chromium:875650 , chromium:851637 ,chromium:b/112859199
TBR=jvanverth@chromium.org

Change-Id: I21e2f158cebeb62dbc38dfafaf9daea314093269
Reviewed-on: https://chromium-review.googlesource.com/1208297
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@{#589064}
[modify] https://crrev.com/f65d3e611c4dce936326bf53b5a065babef1129b/DEPS