Chrome Version: 64.0.3282.190
Chrome OS Version: 10176.76.0
Chrome OS Platform: Pixelbook/eve

Please specify Cr-* of the system to which this bug/feature applies (add
the label below).
?

Steps To Reproduce:
(1) Have pinned app/shortcut (e.g. YouTube web or Gmail web) on shelf
(2) Open said pinned app (which opens in a new tab)
(3) Unpin said pinned app
(4) Close the opened tab from (2)

Expected Result:
Unpinned app/shortcut does not appear in shelf

Actual Result:
Unpinned app/shortcut remains on shelf

How frequently does this problem reproduce? (Always, sometimes, hard to
reproduce?)
Always

What is the impact to the user, and is there a workaround? If so, what is
it?
Almost no impact. Workaround is to unpin when there are no tabs open.