perf top: Show info message while collecting samples

Give visual cue about what is happening while initially collecting the
minimal set of samples to collect/sort/display.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-xcui60p1v6ozijfam2o89ya8@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/ui/browsers/hists.c

@@ -2894,6 +2894,9 @@ static int perf_evsel__hists_browse(struct evsel *evsel, int nr_events,
 	if (symbol_conf.col_width_list_str)
 		perf_hpp__set_user_width(symbol_conf.col_width_list_str);
 
+	if (!is_report_browser(hbt))
+		browser->b.no_samples_msg = "Collecting samples...";
+
 	while (1) {
 		struct thread *thread = NULL;
 		struct map *map = NULL;