perf hists: Introduce output_resort_cb method

When dealing with nested hist entries it's helpful to have a way to
resort those nested objects.

Adding optional callback call into output_resort function and following
new interface function:

  typedef int (*hists__resort_cb_t)(struct hist_entry *he);

  void hists__output_resort_cb(struct hists *hists,
                               struct ui_progress *prog,
                               hists__resort_cb_t cb);

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1470074555-24889-7-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/hist.h b/tools/perf/util/hist.h
index 49aa4fa..0a1edf1 100644
--- a/tools/perf/util/hist.h
+++ b/tools/perf/util/hist.h
@@ -153,8 +153,12 @@
 				   struct perf_hpp_fmt *fmt, int printed);
 void hist_entry__delete(struct hist_entry *he);
 
+typedef int (*hists__resort_cb_t)(struct hist_entry *he);
+
 void perf_evsel__output_resort(struct perf_evsel *evsel, struct ui_progress *prog);
 void hists__output_resort(struct hists *hists, struct ui_progress *prog);
+void hists__output_resort_cb(struct hists *hists, struct ui_progress *prog,
+			     hists__resort_cb_t cb);
 int hists__collapse_resort(struct hists *hists, struct ui_progress *prog);
 
 void hists__decay_entries(struct hists *hists, bool zap_user, bool zap_kernel);