UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:55.0) Gecko/20100101 Firefox/55.0

Steps to reproduce the problem:
1. Create a table with multiple captions
2. Add vertical margins to the captions

What is the expected behavior?
Margins should collapse (see https://drafts.csswg.org/css-tables-3/#ref-for-propdef-caption-side-4).

What went wrong?
Margins do not collapse.

Did this work before? N/A 

Does this work in other browsers? Yes

Chrome version: 60.0.3073.0  Channel: n/a
OS Version: 10.0
Flash Version: Shockwave Flash 25.0 r0

https://jsfiddle.net/ofc3yv4n/

Margins collapse properly on Edge. Firefox does not support multiple captions.
 

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