Here is also a jsfiddle to show the problem and that it only occurs with the exact same rgba values - https://jsfiddle.net/ybx2fdqp/1/

same on my side, only difference i'm on [windows 10], that occured just after updating chrome to v59.

3 tips:
-that happend also for left/right


-seems happend only when the 2 values of the 2 properties is equal and use 
 rgba
ex:(top:1px...; / bottom:2px...;) it work!
ex:(top:...rgba(0,0,0,0.11); / bottom:...rgba(0,0,0,0.12);) it work!
ex:(top:... red; /bottom:... red;) it work!
ex:(top:... rgb(0,0,1); /bottom:... rgb(0,0,1);) it work!

[Mac triage] Over to Blink, though FWIW, this doesn't repro for me in either stable or Canary with the given JSFiddle

I have tryed it on my personnal computer which is also a windows 10 computer, and add a screenshot of the jsfiddle.
-i did it in private mode to exclude any extension
-i also reset all my "chrome://flag" to default

I'll try to find a v58 to try to take a new picture.

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	2017-06-10 00_19_41-.png 92.4 KB View Download

here you ll find a picture with v58 in the same condition.

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	2017-06-10 01_06_35-.png 98.6 KB View Download

On my internal screen on my MacBook it works fine with the borders but as soon as I plug in my external monitor it doesn't work anymore and shows up broken/not visible.

hum?
reading your comment i've just take a look on my GPU driver.
That was not up to date... i have a 980 GTX ti, and i updated driver to v382.53 and after that everything appear fine, has you can see on the picture.

I dont really understand why because i thought only few css properties using  GPU.

I'll test it tomorrow on my computer at work.

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Tested the issue on Mac os 10.12.5 using chrome M59 #59.0.3071.86 and M58 #58.0.3029.110 and observed different behavior as attached in screenshots.

@nils.berenbold-- Could you please check attached screenshot and confirm if M58 behavior is the expected behavior , so that we can continue bisecting the issue.

Thanks!

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	M58Behavior-730489.png 196 KB View Download

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	M59Behavior-730489.png 189 KB View Download

Here's a test case for the bug. Can reproduce with minimal css.

https://jsfiddle.net/xz9euh4y/

This is currently breaking pretty much all production sites I've worked on since rgba spec was implemented. As an outsider I would call this high priority.

@hdodda@chromium.org

Yep the 58 is how it should look, correct.

Thank you for providing more feedback. Adding requester "hdodda@chromium.org" to the cc list and removing "Needs-Feedback" label.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Tested the issue on mac os 10.12.5 using chrome M59 #59.0.3071.86 and issue is reproduced.

This is a regression issue broken in M60 and is fixed in latest beta dev and canary channels.

It is reproduced only on Mac OS.

Using the old bisect script providing the reverse bisect results,
Good build: 60.0.3096.0(Revision: 470759).
Bad build: 60.0.3094.0 (Revision: 470111).

You are probably looking for a change made after 470313 (known good), but no later than 470324 (first known bad).

CHANGELOG URL:
  https://chromium.googlesource.com/chromium/src/+log/1073d1c2e24a31bc6c34bbc6a6c198ae5d668086..175ceeff6a099a7923928ba8fcd58c6b80563251

Unable to find the actual suspect from the above cl , 

@could someone please help us in finding the actual suspect.

Thanks!

I got the same problem on Win10 aswell, with 59.0.3071.86 (Offizieller Build) (64-Bit) (Kohorte: 59_86_Win)

Suspecting Skia roll from the unregression range:
https://chromium.googlesource.com/chromium/src/+/175ceeff6a099a7923928ba8fcd58c6b80563251

I'm looking into the changes- let me get Brian on this in case he (or Mike) are aware of something they've changed lately in our color processing that could be the culprit.

that working now for me with Version 60.0.3112.78 (Official Build) (64-bit)

This issue has been Available for over a year. If it's no longer important or seems unlikely to be fixed, please consider closing it out. If it is important, please re-triage the issue.

Sorry for the inconvenience if the bug really should have been left as Available.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

This issue has an owner, a component and a priority, but is still listed as untriaged or unconfirmed. By definition, this bug is triaged. Changing status to "assigned". Please reach out to me if you disagree with how I've done this.