Remove unused windowAttributes

Historically used for window insets, then later for watch roundedness as
well, then only watch roundedness, and finally nothing at all except
recycle().

See I24e6564030a6051c3ac7262868983b43e13eee65 for the point where this
became totally unused.

Change-Id: Ic03a94a90cbf0b9fc61df190b106747d096b94c4