UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36

Steps to reproduce the problem:
Reduced test case for table elements
1. Go to https://jsfiddle.net/574v2eyg/
2. The `th` elements have sticky position while scrolling the entire `tbody`.
3. Click the "Add more rows" button.
4. Observe that the `th` elements scroll out of view when scrolling to the appended rows.

Reduced test case for non-table elements
1. Go to https://jsfiddle.net/utxywmg2/
2. The `header` element has sticky position while scrolling the original `p` elements.
3. Click the "Add more paragraphs" button.
4. Observe that the `header` element scrolls out of view when scrolling to the appended paragraphs.

What is the expected behavior?
Elements with position:sticky should continue to be sticky when new elements are added that affect the scroll height of the container.

What went wrong?
Adding new elements that affect the scroll height of the container causes elements with position:sticky to behave as if the scrolling container itself is being scrolled out of view.

Did this work before? N/A 

Does this work in other browsers? N/A

Chrome version: 56.0.2924.87  Channel: stable
OS Version: CentOS Linux release 7.3.1611 (Core)
Flash Version: Shockwave Flash 24.0 r0

I searched through other bug reports related to position:sticky. Some of them sound possibly related, but it's very difficult to tell for sure.