stylecontext: Split out GtkCssNode into own file

The functionality of it is supposed to grow, so better put it in a
custom file early.

This is just a naive split so far, the next patches will split things
further.

gtk/gtkcssnode.c

@@ -0,0 +1,69 @@
+/* GTK - The GIMP Toolkit
+ * Copyright (C) 2014 Benjamin Otte <otte@gnome.org>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include "gtkcssnodeprivate.h"
+
+GtkCssNode *
+gtk_css_node_new (void)
+{
+  GtkCssNode *cssnode;
+
+  cssnode = g_slice_new0 (GtkCssNode);
+  cssnode->decl = gtk_css_node_declaration_new ();
+
+  return cssnode;
+}
+
+void
+gtk_css_node_free (GtkCssNode *cssnode)
+{
+  if (cssnode->style)
+    g_object_unref (cssnode->style);
+  gtk_css_node_declaration_unref (cssnode->decl);
+  g_slice_free (GtkCssNode, cssnode);
+}
+
+GtkCssNode *
+gtk_css_node_get_parent (GtkCssNode *cssnode)
+{
+  return cssnode->parent;
+}
+
+void
+gtk_css_node_set_style (GtkCssNode  *cssnode,
+                        GtkCssStyle *style)
+{
+  if (cssnode->style == style)
+    return;
+
+  if (style)
+    g_object_ref (style);
+
+  if (cssnode->style)
+    g_object_unref (cssnode->style);
+
+  cssnode->style = style;
+}
+
+GtkCssStyle *
+gtk_css_node_get_style (GtkCssNode *cssnode)
+{
+  return cssnode->style;
+}
+