[Affected versions]: -64.0a1 (2018-10-11), 63.0b13, 62.0.3, 55.0, 60.2.2esr ; [Affected platforms]: - Win10, macOS0.13, Ubuntu 16.04 [Steps to reproduce]: 1. Launch Firefox; 2. Open the DevTools; 3. Click on the RDM button; 4. Click on the Edit List button; 5.a Grab the Devtools section and drag it up (devTools must be docked at bottom); 5.b Grab the browser and shrink its height; [Expected result]: - the list modal should adjust its size, scrollbar could be enabled once height doesn't allow for the whole content to be displayed; [Actual result]: - modal has a fixed height; - modal is pushed up; - the Done button is covered up b the DevTools section when docked at bottom and is unclickable; [Regression range]: - does not seem to be a regression; - noticed that on version 55 this feature has been added and it didn't have the resize at all; [Additional notes]: - attached screen recording with the issue; - scaling horizontally brings up