[sysprof] callgraph: add column headers in screenshot text

[Christian Hergert <chergert src gnome org>]

commit 66d4bb25e17ec586384b6778b980e989c61e574e
Author: Christian Hergert <christian hergert me>
Date:   Wed Apr 13 20:58:44 2016 -0700

    callgraph: add column headers in screenshot text

 lib/sp-callgraph-view.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/lib/sp-callgraph-view.c b/lib/sp-callgraph-view.c
index c31dec6..d689412 100644
--- a/lib/sp-callgraph-view.c
+++ b/lib/sp-callgraph-view.c
@@ -957,7 +957,7 @@ sp_callgraph_view_screenshot (SpCallgraphView *self)
    * put the timing information at the beginning of the line.
    */
 
-  str = g_string_new (NULL);
+  str = g_string_new ("      SELF CUMULATIVE    FUNCTION\n");
   tree_path = gtk_tree_path_new_first ();
 
   for (;;)