I suspect this regressed after bug 856665 landed. Patch coming.
Created attachment 762681 [details] [diff] [review]
We just blindly doubled the coordinates for the bookmarks menu button, assuming that Toolbar@2x was the same as Toolbar...
Well, it's not. At least, not for now. The WebRTC button is missing from Toolbar@2x.
This'll all get sorted once bug 877335 lands. In the meantime, this is a stopgap fix.