Steps to reproduce: 1) Create non-maximized window. 2) Maximize. 3) Unmaximize. 4) Pin the tab 5) Maximize. 6) Unmaximize. Expected result: * No blank space in the tab bar on the left of the tabs. Actual result: 1) There is a phantom space to the left of the tab about the size of a pinned tab. 2&5) After the window is maximized the tab bar shifts left and the phantom vanishes. 3&6) After the window is unmaximized the tab bar shifts right and a phantom appears. Aside from the inconsistent placement of pinned tabs and the change from previous versions, the shifting after (un)maximizing is annoying. Firefox Nightly on Xubuntu. Reproduced with a new profile.