Add thermal category to atrace.

Thermal has become more and more interesting when study
application/system behavior. This CL adds a new thermal
category into atrace.

Bug: 160818586
Test: take systrace
Change-Id: Ia64ddebfc821fb3d48c7b888ca84cf970eebff77
(cherry picked from commit 86d46df5)
Merged-In: Ia64ddebfc821fb3d48c7b888ca84cf970eebff77