[Note]: - Logged based on Bug 1241720 Comment 25 [Affected versions]: - 49.0a1 (2016-05-03) [Affected platforms]: - Windows 7 x64, Ubunutu 14.04 x86 [Steps to reproduce]: 1. Launch Firefox. 2. From about:config, enable the devtools.responsive.html.enabled pref. 3. Open RDM. 4. Click the 'no device selected' button. 5. Click the 'Edit list...' button and observe the scrollbars. [Expected result]: - The scrollbars are correctly displayed on the edge of the modal. [Actual result]: - The scrollbars are not correctly positioned (see the attached screenshot). [Regression range]: - This is not a regression since this is a new implementation. [Additional notes]: - Note that on Mac OS X the scrollbars are not available.

So, I feel we should maybe increase the width/height for the different OS.

Yes, we should at least try to increase the width so that horizontal scrolling is not needed. We could do the height as needed as well. :gl also mentioned there are some devices in the list we actually want to hide, so changing that should reduce at least the height.

This issue is still reproducible on Firefox 52 RC, but only under Ubuntu 16.04x64 OS. Under Windows 10x64 and under Mac OS X 10.11.6, the issue is no longer reproducible, since there is no scrollbar available in the modal.