am 9b516383: am e35d9280: cherrypick from jb-dev Change-Id: Idecee238d8872ca1c32a80d13ad61bacf89c39f7 docs: Systrace tool documentation

* commit '9b5163836ccf121af89040c1e465a3f96d37aa7b':
  cherrypick from jb-dev Change-Id: Idecee238d8872ca1c32a80d13ad61bacf89c39f7 docs: Systrace tool documentation