Chrome Version: 66.0.3359.139 (Official Build) (64-bit)
OS: Linux

What steps will reproduce the problem?
(1) Open a PDF
(2) Click on a link in the PDF that brings you to another place in the same PDF (e.g. the Table of Contents or a link to a bibliography entry)
(3) Click the back button

What is the expected result?

When I click the back button, it takes me back to the place in the PDF I was previously.

What happens instead?
The previous webpage I was on gets loaded (and I have to go back forward, reload the PDF, and scroll from the beginning to get back to where I was).


(Note: I don't believe this is a regression. It just seems like a broken experience)