Covariant return types for View’s onSaveInstanceState

When implementing custom Views that use the onSaveInstanceState hook, consider exposing the final Parcelable implementation.

Knowing the final type of a Parcelable instance is helpful, especially for consumers who save the View tree manually (not using Android’s Window traversal). Consumers of a custom View who use the onSaveInstanceState hook can make use of this knowledge if onSaveInstanceState uses Java’s covariance and returns the View’s implementation of the Parcelabale saved state (e.g. @Override public MyProfileView.SavedState onSaveInstanceState()).