Steps to reproduce:

1. Edit or create a page;
2. Open Edit mode;
3. Enlarge the browser window;
4. Try to move the Elements panel further then the window was
   Actual Result: It is impossible to move Elements panel
   Expected Result: the Elements panel should be possible to move in new size of the browser window
   Please see attached animation for more information.

Reproduced on: MacOS 10.13.6, Chrome 68.0.3440.106