Chrome Version: 61.x
OS: Linux (all?)

What steps will reproduce the problem?
(1) Load a PDF in the Chrome PDF Viewer
(2) Go to settings and change the font size
(3) Go back to the tab with the PDF

What is the expected result?

Chrome PDF Viewer UI should have changed due to the font size preference change.

What happens instead?

Nothing.

If one reloads the tab with the PDF, then the change takes affect.

This is part (b) of https://bugs.chromium.org/p/chromium/issues/detail?id=541068#c6