It's part of the code cleanup, to make the XML attributes conform to the
Java setter/getter properties and vice versa.
Setting a background in XML is done through the *android:background*attribute.
The corresponding setter of the attribute in Java was *setBackgroundDrawable
The two attribute names are not the same: *drawable *vs *backgroundDrawable*
They decided to make them the same by changing the Java name of this
attribute to *drawable *as well, resulting in a setter called *setDrawable*.