tracefs not debugfs

Test:   Device boots
        Can take photos
        Run "adb shell atrace -c -b 16000 -t 5 gfx" without root and check produces
        output
        Run "python systrace.py view gfx freq sched am wm dalvik
        binder_driver" from external/chromium-trace after adb root and
        check populated
Bug: 31856701
Change-Id: Ic319f8a0a3e395efa7ee8ba33a868ac55cb44fe4