Repurpose doze wake lock stats for draw wake lock instead.

The doze wake lock is an internal implementation detail with no
power impact.  However the draw wake lock is much more interesting
to track because it's essentially like a special purpose partial
wake lock which may be acquired while dozing.

Bug: 21949905
Change-Id: Iedd5f366eb010a47a9691374c5cd3d85ea68173d