Also, on iOS 8.0+, use `+[NSLayoutConstraint activateConstraints:]` and `+deactivateConstraints:` to efficiently prevent redundant constraints from lingering. Fixes #1779.
Also, on iOS 8.0+, use `+[NSLayoutConstraint activateConstraints:]` and `+deactivateConstraints:` to efficiently prevent redundant constraints from lingering. Fixes #1779.