On Windows 7, when using Private browsing mode, the three system buttons on the top-right corner seems to be a couple of pixels too low and have strange effect. See the joined screnshots with the light and dark themes. However it's less visible on screenshots and it's better to test directly. Bug seems to affect all three Firefox themes and density. It's with Aero, I didn't tested basic or classic Windows themes. Bug reproduced using clean profile on latest Nightly. Stable isn't affected, this might be a Photon bug.

This looks like another variation of bug 1396240. If you run this build, is it better: https://queue.taskcluster.net/v1/task/GoTqPtt8RFK1wm2UiE5u2A/runs/0/artifacts/public/build/target.zip ? The backout that closes that bug (see bug 1383051) isn't on mozilla-central yet, so it won't be in today's early nightly. Maybe the later one or tomorrow -- hence suggesting the specific build from mozilla-inbound.

(In reply to :Gijs from comment #3) > This looks like another variation of bug 1396240. If you run this build, is > it better: > https://queue.taskcluster.net/v1/task/GoTqPtt8RFK1wm2UiE5u2A/runs/0/ > artifacts/public/build/target.zip ? > > The backout that closes that bug (see bug 1383051) isn't on mozilla-central > yet, so it won't be in today's early nightly. Maybe the later one or > tomorrow -- hence suggesting the specific build from mozilla-inbound. Yes the bug isn't here with this build. However the build you linked here is using the old rectangular Private Browsing indicator, not the circular one.

(In reply to Clément Lefèvre from comment #4) > (In reply to :Gijs from comment #3) > > This looks like another variation of bug 1396240. If you run this build, is > > it better: > > https://queue.taskcluster.net/v1/task/GoTqPtt8RFK1wm2UiE5u2A/runs/0/ > > artifacts/public/build/target.zip ? > > > > The backout that closes that bug (see bug 1383051) isn't on mozilla-central > > yet, so it won't be in today's early nightly. Maybe the later one or > > tomorrow -- hence suggesting the specific build from mozilla-inbound. > > Yes the bug isn't here with this build. > However the build you linked here is using the old rectangular Private > Browsing indicator, not the circular one. Yes, I think that's deliberate - the patch that changed it to be round is getting backed out (that's bug 1383051, AIUI).

(In reply to :Gijs from comment #5) > (In reply to Clément Lefèvre from comment #4) > > (In reply to :Gijs from comment #3) > > > This looks like another variation of bug 1396240. If you run this build, is > > > it better: > > > https://queue.taskcluster.net/v1/task/GoTqPtt8RFK1wm2UiE5u2A/runs/0/ > > > artifacts/public/build/target.zip ? > > > > > > The backout that closes that bug (see bug 1383051) isn't on mozilla-central > > > yet, so it won't be in today's early nightly. Maybe the later one or > > > tomorrow -- hence suggesting the specific build from mozilla-inbound. > > > > Yes the bug isn't here with this build. > > However the build you linked here is using the old rectangular Private > > Browsing indicator, not the circular one. > > Yes, I think that's deliberate - the patch that changed it to be round is > getting backed out (that's bug 1383051, AIUI). But it should come back with a round form, right? So I guess it should be taken care of that either.