perf tools: Mark branch_info maps as referenced

As noticed by Jiri, the hist_entry->branch_info.to/from maps need to be
marked as referenced to avoid problems later on.  So we do this when the
hist_entry is allocated.
Signed-off-by: Stephane Eranian <eranian@google.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20130114140245.GA4692@quadSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/hist.c

@@ -245,6 +245,14 @@ static struct hist_entry *hist_entry__new(struct hist_entry *template)
 
 		if (he->ms.map)
 			he->ms.map->referenced = true;
+
+		if (he->branch_info) {
+			if (he->branch_info->from.map)
+				he->branch_info->from.map->referenced = true;
+			if (he->branch_info->to.map)
+				he->branch_info->to.map->referenced = true;
+		}
+
 		if (symbol_conf.use_callchain)
 			callchain_init(he->callchain);