Add tests for hasAlpha and isPremultiplied.

reconfigure(), setHasAlpha(), and setIsPremultiplied() can modify the
return values of hasAlpha() and isPremultiplied(). Add tests to verify
that they change the values in ways we expect.

Depends on I91fc1f1e46e9294364b1af0ab4bdb37c68d7058e

Change-Id: Ib7066e4c512d8737725d0c30285d965ba9bddddd