Revert "New tests for the new MipmapDrawable class."

Bug 3285373

This reverts commit 4e19452bb42984178390f65028afe38e2cf55cf0.

The class is now hidden in HC. However, it's great to see that new tests
are being added!

Change-Id: Ibfd1b8a585a6b2c81a1eb261a432f91207f66484
4 files changed