Add backtrace info to the CPU usage timechart.

Signed-off-by: Stanislav Fomichev <stfomichev@yandex-team.ru>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ramkumar Ramachandra <artagnon@gmail.com>
Link: http://lkml.kernel.org/r/1385995056-20158-2-git-send-email-stfomichev@yandex-team.ru


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>