Chrome Version: (copy from chrome://version)
OS: (e.g. Win10, MacOS 10.12, etc...)

What steps will reproduce the problem?
(1) Visit https://jsfiddle.net/ujn51d32/ , on a platform where scrollbars take up space (not on Mac).

(2) Resize your window's width (or really just the results jsfiddle pane).

What is the expected result?
Rendering shouldn't change.

What happens instead?
The scrollbar (on the .scrollable box around the teal element) rapidly appears & disappears -- it seems to oscillate between off/on, for each (window-resize-triggered) reflow.
 

Chrome Version: Google Chrome	71.0.3554.4 (Official Build) dev (64-bit)
OS: Ubuntu 18.04 (Linux)

What steps will reproduce the problem?
(1) Visit https://jsfiddle.net/ujn51d32/ , on a platform where scrollbars take up space (not on Mac).

(2) Resize your window's width (or really just the results jsfiddle pane).

What is the expected result?
Rendering shouldn't change.

What happens instead?
The scrollbar (on the .scrollable box around the teal element) rapidly appears & disappears -- it seems to oscillate between off/on, for each (window-resize-triggered) reflow.