perf report/top: Add menu entry for toggling callchain expansion

Since previously pressing ENTER toggled expansion/collapse of callchain
entries and now brings up the same menu used when callchains are not
present, add an entry so that users can quickly figure out the change in
behaviour.

Its worth mentioning that we also always had 'e'/'c' to expand/collapse
all entries in a hist entry and 'E'/'C' for all hist entries.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-f9o03jo29fypvd8ly3j49d36@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/ui/browsers/hists.c

@@ -2527,6 +2527,26 @@ add_dso_opt(struct hist_browser *browser, struct popup_action *act,
 	return 1;
 }
 
+static int do_toggle_callchain(struct hist_browser *browser, struct popup_action *act __maybe_unused)
+{
+	hist_browser__toggle_fold(browser);
+	return 0;
+}
+
+static int add_callchain_toggle_opt(struct hist_browser *browser, struct popup_action *act, char **optstr)
+{
+	struct hist_entry *he = browser->he_selection;
+
+        if (!he->has_children)
+                return 0;
+
+	if (asprintf(optstr, "Expand/Collapse callchain") < 0)
+		return 0;
+
+	act->fn = do_toggle_callchain;
+	return 1;
+}
+
 static int
 do_browse_map(struct hist_browser *browser __maybe_unused,
 	      struct popup_action *act)
@@ -3137,6 +3157,7 @@ static int perf_evsel__hists_browse(struct evsel *evsel, int nr_events,
 					     &options[nr_options], thread);
 		nr_options += add_dso_opt(browser, &actions[nr_options],
 					  &options[nr_options], map);
+		nr_options += add_callchain_toggle_opt(browser, &actions[nr_options], &options[nr_options]);
 		nr_options += add_map_opt(browser, &actions[nr_options],
 					  &options[nr_options],
 					  browser->selection ?