craig.francis@ Thanks for the issue.

Able to reproduce this issue on Windows 10, Mac OS 10.13.3 and Ubuntu 17.10 on the reported version 70.0.3538.77 and latest Canary 72.0.3591.0.

Bisect Information:
===================
Good Build: 69.0.3476.0
Bad Build : 69.0.3477.0

By running per-revision script 'No enough builds error' was coming up, hence below is the ChangeLog URL by running the Chromium bisect.
https://chromium.googlesource.com/chromium/src/+log/7a73f750e5926164aa3ecf077ca5aab8c4eeb28e..6e617e7fd9479367c5d0f50018767a71b7022587

From the above Changelog, suspecting the below change:
Reviewed-on: https://chromium-review.googlesource.com/1112563

schenney@ Please check and confirm if this issue is related to your change, else help us in assigning to the right owner.

Thanks..

Also faced with this problem. It affects background-image rendering canvas if element's with fractional element size (i.e. 10.7px; ). Tho, it does not affects background-color rendering.

Also element with fractional size will not cause overflow on parent element.

Did a pen to better describe it.

https://codepen.io/SDemonUA/pen/RevpGW

background-repeat: no-repeat as a workaround:

https://codepen.io/anon/pen/aQZbVN

Deleted: GIF.gif 53.0 KB

	GIF.gif 53.0 KB View Download

Thanks for the `background-repeat: no-repeat` workaround... am curious how that works.

I think this is a duplicate but I won't mark as such until I confirm that fixing one fixes the other.

Not fixed by https://crrev.com/1c633d483b5e6777fe2ffc5cea93398083638f6e

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2eed6201bd9ed2c65c7910402d32c036db257fb6

commit 2eed6201bd9ed2c65c7910402d32c036db257fb6
Author: Stephen Chenney <schenney@chromium.org>
Date: Sat Dec 15 04:08:07 2018

Fix gradient background sizing

This is a hard-to-fix situation. We size generated background images
according to the tile size, which is a snapped rectangle sized according
to the destination values, in general. But then we compute a src rect
for image drawing using the unsnapped values, because that is best for
bitmap images where we want to pull out the most accurate src rect
possible. However, that source rect ends up larger than the tile size
due to rounding without the original offset in the layer (because now
we are working in image space).

The gradient painting code then sees that it has a src rect that is
larger than the tile size and hence the gradient image size. The code
thinks that we want to have some more pixels than the gradient
provides, which is true in some cases, and scales things to get those
extra pixels in the painted output. Hence empty pixels on the screen
when we really want the gradient to be filling the dest rect.

Changing the gradient painting code will break valid use cases. Changing
the tile size breaks things in a different way and doesn't really fix
the problem. So change the src rect computation to use snapped sizes
for generated content in an attempt to get a src that matches the tile
size.

R=fmalita@chromium.org

Bug:  898950 
Change-Id: I100575ad4f4fa3004fbc232a72c90b0032ccef4e
Reviewed-on: https://chromium-review.googlesource.com/c/1376814
Commit-Queue: Stephen Chenney <schenney@chromium.org>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616944}
[modify] https://crrev.com/2eed6201bd9ed2c65c7910402d32c036db257fb6/third_party/blink/renderer/core/paint/box_painter_base.cc
[add] https://crrev.com/2eed6201bd9ed2c65c7910402d32c036db257fb6/third_party/blink/web_tests/external/wpt/css/css-backgrounds/background-gradient-subpixel-fills-area.html
[add] https://crrev.com/2eed6201bd9ed2c65c7910402d32c036db257fb6/third_party/blink/web_tests/external/wpt/css/css-backgrounds/reference/background-gradient-subpixel-fills-area-ref.html
[modify] https://crrev.com/2eed6201bd9ed2c65c7910402d32c036db257fb6/third_party/blink/web_tests/platform/mac-mac10.10/fast/forms/select/listbox-appearance-basic-expected.png
[modify] https://crrev.com/2eed6201bd9ed2c65c7910402d32c036db257fb6/third_party/blink/web_tests/platform/mac-mac10.11/fast/forms/select/listbox-appearance-basic-expected.png
[modify] https://crrev.com/2eed6201bd9ed2c65c7910402d32c036db257fb6/third_party/blink/web_tests/platform/mac-mac10.12/fast/forms/select/listbox-appearance-basic-expected.png
[modify] https://crrev.com/2eed6201bd9ed2c65c7910402d32c036db257fb6/third_party/blink/web_tests/platform/mac/fast/forms/select/listbox-appearance-basic-expected.png
[modify] https://crrev.com/2eed6201bd9ed2c65c7910402d32c036db257fb6/third_party/blink/web_tests/platform/mac/svg/zoom/page/zoom-background-images-expected.png
[modify] https://crrev.com/2eed6201bd9ed2c65c7910402d32c036db257fb6/third_party/blink/web_tests/platform/win/svg/zoom/page/zoom-background-images-expected.png

 Issue 899515  has been merged into this issue.

 Issue 897441  has been merged into this issue.

 Issue 918168  has been merged into this issue.

 Issue 920786  has been merged into this issue.