perf ui: New hists tree widget

The stock newt checkbox tree widget we were using was not really
suitable for hist entry + callchain browsing.

The problems with it were manifold:

- We needed to traverse the whole hist_entry rb_tree to add each entry +
  callchains beforehand.

- No control over the colors used for each row

So a new tree widget, based mostly on slang, was written.

It extends the ui_browser class already used for annotate to allow the
user to fold/unfold branches in the callchains tree, using extra fields
in the symbol_map class that is embedded in hist_entry and
callchain_node instances to store the folding state and when changing
this state calculates the number of rows that are produced when showing
a particular hist_entry instance.

This greatly speeds up browsing as we don't have to upfront touch all
the entries and only calculate callchain related operations when some
callchain branch is actually unfolded.

The memory footprint is also reduced as the data structure is not
duplicated, just some extra fields for controling callchain state and to
simplify the process of seeking thru entries (nr_rows, row_offset) were
added.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/hist.c

@@ -885,6 +885,9 @@ static void hists__remove_entry_filter(struct hists *self, struct hist_entry *h,
 		return;
 
 	++self->nr_entries;
+	if (h->ms.unfolded)
+		self->nr_entries += h->nr_rows;
+	h->row_offset = 0;
 	self->stats.total_period += h->period;
 	self->stats.nr_events[PERF_RECORD_SAMPLE] += h->nr_events;
 

tools/perf/util/sort.h

@@ -38,6 +38,12 @@ extern struct sort_entry sort_sym;
 extern struct sort_entry sort_parent;
 extern enum sort_type sort__first_dimension;
 
+/**
+ * struct hist_entry - histogram entry
+ *
+ * @row_offset - offset from the first callchain expanded to appear on screen
+ * @nr_rows - rows expanded in callchain, recalculated on folding/unfolding
+ */
 struct hist_entry {
 	struct rb_node		rb_node;
 	u64			period;
@@ -50,6 +56,12 @@ struct hist_entry {
 	u64			ip;
 	s32			cpu;
 	u32			nr_events;
+
+	/* XXX These two should move to some tree widget lib */
+	u16			row_offset;
+	u16			nr_rows;
+
+	bool			init_have_children;
 	char			level;
 	u8			filtered;
 	struct symbol		*parent;

tools/perf/util/symbol.h

@@ -102,6 +102,8 @@ struct ref_reloc_sym {
 struct map_symbol {
 	struct map    *map;
 	struct symbol *sym;
+	bool	      unfolded;
+	bool	      has_children;
 };
 
 struct addr_location {