timebasedwidget: restore scroll when using "toggle show all"

"Toggle Show All" would restore only the scale. Now it sets/restores the
scroll as well.

app/widget/timebased/timebased.cpp

@@ -447,7 +447,7 @@ void TimeBasedWidget::ToggleShowAll()
 
   if (toggle_show_all_) {
     SetScale(toggle_show_all_old_scale_);
-    toggle_show_all_ = false;
+    scrollbar_->setValue(toggle_show_all_old_scroll_);
   } else {
     int w;
 
@@ -460,9 +460,13 @@ void TimeBasedWidget::ToggleShowAll()
     w = w / 10 * 9;
 
     toggle_show_all_old_scale_ = GetScale();
+    toggle_show_all_old_scroll_ = scrollbar_->value();
+
     SetScale(w / GetConnectedNode()->GetLength().toDouble());
-    toggle_show_all_ = true;
+    scrollbar_->setValue(0);
   }
+
+  toggle_show_all_ = !toggle_show_all_;
 }
 
 void TimeBasedWidget::GoToIn()

app/widget/timebased/timebased.h

@@ -168,6 +168,7 @@ private:
   bool toggle_show_all_;
 
   double toggle_show_all_old_scale_;
+  int toggle_show_all_old_scroll_;
 
 private slots:
   void UpdateMaximumScroll();