am c80188eb: am 9b516383: am e35d9280: cherrypick from jb-dev Change-Id: Idecee238d8872ca1c32a80d13ad61bacf89c39f7 docs: Systrace tool documentation

* commit 'c80188ebefbcbe8448fdab0a9f44f02f770f6e8a':
  cherrypick from jb-dev Change-Id: Idecee238d8872ca1c32a80d13ad61bacf89c39f7 docs: Systrace tool documentation