Delete dead code

Bug: 22378829

Every time setText is called a BoringLayout is created.
BoringLayout internally creates a new Paint called mWorkPaint.

However, creating a Paint turns out to be somewhat substantial
amount of work, and mWorkPaint is never actually used. Deleting
this shaves off roughly 50ms and 1,000 object creations during
a fling on a listview.

Change-Id: I5d03402b9027df6ce0f3e58160752c66c69a4d2d