User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:57.0) Gecko/20100101 Firefox/57.0 Build ID: 20170917220255 Steps to reproduce: Upgraded to Nightly 57.0a1 (20170912013600). Not exactly sure which build, but somewhere around 9/10 or 9/11 nightly builds. Actual results: Several UI elements are not being drawn correctly. - The window title bar appears with a solid black background with a small gray rectangle in the top left and top right of the title bar edges. - The page title of web pages visited, draws in a very hard to read light gray and draws over the over the top of tab titles. Expected results: The title bar should appear using the same standard macOS color scheme familiar to Mac users. It should not be all black and the page titles should not draw over the top of the tab titles.

screen shots of several Nightly windows with the incorrect color scheme, gray blocks in top edge corners, and page title and tab title text overlapping. NOTE: The screen shot doesn't show correctly that the title bar is completely black when displayed on screen. In the screen shot only the bottom 3/4 of the title bar is black. On a Retina display, Cinema display and iMac non-retina, the title bar is all black. (first time I've seen a screen shot not match 100% whats on screen).

macOS regression: - This does occur on macOS High Sierra GM candidate 10.13 (17a362a) + Does not occur on macOS Sierra 10.11.6 (15g1611) + Does not occur on macOS El Capitan 10.12.6 (16g29)