Since bug 177805 landed, when the user has a high resolution (high dpi) display, we change the meaning of a CSS pixel so that it is multiple physical pixels and scale everything up. This is a tracking bug for issues that occur only in this mode, or that cause particularly bad problems in it.
Marking all tracking bugs which haven't been updated since 2014 as INCOMPLETE. If this bug is still relevant, please reopen it and move it into a bugzilla component related to the work being tracked. The Core: Tracking component will no longer be used.