Added DrawableWrapperTest

Mostly borrowed logic from ScaleDrawableTest, which tests the same
kinds of things. Some tests eliminated because they were irrelevant for
this abstract base class. Some logic changed because behavior of
some things like onLevelChange() are different for DrawableWrapper.

Issue #21664864  [CTS] Add tests for DrawableWrapper

Change-Id: I6d1ab87765eeaf61586fc93701f3b3bf5192e33b
1 file changed