[gnome-calculator] Use a header bar on the preferences dialog

[Arth Patel <arthpatel src gnome org>]

commit 19f4ac6ae5201d8c5276af7fa116f4219d2f7562
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Fri May 9 20:44:09 2014 -0500

    Use a header bar on the preferences dialog
    
    https://bugzilla.gnome.org/show_bug.cgi?id=729903

 src/math-preferences.vala |   14 +++++++++-----
 1 files changed, 9 insertions(+), 5 deletions(-)
---
diff --git a/src/math-preferences.vala b/src/math-preferences.vala
index 51b8582..cccc143 100644
--- a/src/math-preferences.vala
+++ b/src/math-preferences.vala
@@ -10,7 +10,8 @@
 
 public class MathPreferencesDialog : Gtk.Dialog
 {
-    private MathEquation equation;
+    public MathEquation equation { private get; construct; }
+
     private Gtk.ComboBox angle_unit_combo;
     private Gtk.ComboBox number_format_combo;
     private Gtk.ComboBox word_size_combo;
@@ -18,15 +19,18 @@ public class MathPreferencesDialog : Gtk.Dialog
     private Gtk.CheckButton thousands_separator_check;
     private Gtk.CheckButton trailing_zeroes_check;
 
-    public MathPreferencesDialog (MathEquation equation)
+    public MathPreferencesDialog (MathEquation eq)
     {
-        this.equation = equation;
+        Object(use_header_bar: 1, equation: eq);
+    }
 
+    construct
+    {
         set_title (/* Title of preferences dialog */
                    _("Preferences"));
         border_width = 8;
-        add_button (/* Label on close button in preferences dialog */
-                    _("_Close"), 0);
+
+        ((Gtk.HeaderBar) get_header_bar ()).show_close_button = true;
 
         var grid = new Gtk.Grid ();
         grid.show ();