Chrome Version: 60.0.3112.101 
OS: Linux

What steps will reproduce the problem?
(1) Go onto https://diply.com/redonkulous-tattoos/5?publisher=bert
(2) Create an Intersection Observer: new IntersectionObserver((entries) => {console.log("entries", entries);})
(3) Observe the div with ID "div-da-content1"
(4) Look at the dimensions for IntersectionRect and BoundingClientRect in the entry. There is an off by one error.

See https://groups.google.com/a/google.com/forum/#!topic/ads-latency-infra/vj8-Xl5xOUs

What is the expected result?
The top, right, bottom and left values should be the same for IntersectionRect and BoundingClientRect since the div is fully onscreen.

What happens instead?
The IntersectionRect top is 289, while the BoundingClientRect top is 290 (at least those are the dimensions for my screensize).

Note I've only been able to reproduce this on my workstation, not my laptop (OSX).

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For graphics-related bugs, please copy/paste the contents of the about:gpu
page at the end of this report.