Add size negotiation to the tray icons

* Rename ShellGtkWindowActor to ShellGtkEmbed, and make it require
  a ShellEmbeddedWindow rather than a general GtkWindow.

* Add ShellEmbeddedWindow subclass of GtkWindow that bypasses most
  of the GtkWindow complexity for size negotiation, and calls out
  to a clutter actor instead; also automatically handle reparenting
  the GtkWindow into the stage window.

* Use the reworked ShellGtkEmbed in ShellTrayManager, this simplifies
  the code a bit, and more importantly results in the tray icons
  having the correct size negotiation, rather than having a fixed
  24x24 size.

http://bugzilla.gnome.org/show_bug.cgi?id=580047

src/shell-embedded-window.h

@@ -0,0 +1,33 @@
+#ifndef __SHELL_EMBEDDED_WINDOW_H__
+#define __SHELL_EMBEDDED_WINDOW_H__
+
+#include <gtk/gtk.h>
+
+#define SHELL_TYPE_EMBEDDED_WINDOW                 (shell_embedded_window_get_type ())
+#define SHELL_EMBEDDED_WINDOW(obj)                 (G_TYPE_CHECK_INSTANCE_CAST ((obj), SHELL_TYPE_EMBEDDED_WINDOW, ShellEmbeddedWindow))
+#define SHELL_EMBEDDED_WINDOW_CLASS(klass)         (G_TYPE_CHECK_CLASS_CAST ((klass), SHELL_TYPE_EMBEDDED_WINDOW, ShellEmbeddedWindowClass))
+#define SHELL_IS_EMBEDDED_WINDOW(obj)              (G_TYPE_CHECK_INSTANCE_TYPE ((obj), SHELL_TYPE_EMBEDDED_WINDOW))
+#define SHELL_IS_EMBEDDED_WINDOW_CLASS(klass)      (G_TYPE_CHECK_CLASS_TYPE ((klass), SHELL_TYPE_EMBEDDED_WINDOW))
+#define SHELL_EMBEDDED_WINDOW_GET_CLASS(obj)       (G_TYPE_INSTANCE_GET_CLASS ((obj), SHELL_TYPE_EMBEDDED_WINDOW, ShellEmbeddedWindowClass))
+
+typedef struct _ShellEmbeddedWindow        ShellEmbeddedWindow;
+typedef struct _ShellEmbeddedWindowClass   ShellEmbeddedWindowClass;
+
+typedef struct _ShellEmbeddedWindowPrivate ShellEmbeddedWindowPrivate;
+
+struct _ShellEmbeddedWindow
+{
+  GtkWindow parent;
+
+  ShellEmbeddedWindowPrivate *priv;
+};
+
+struct _ShellEmbeddedWindowClass
+{
+  GtkWindowClass parent_class;
+};
+
+GType shell_embedded_window_get_type (void) G_GNUC_CONST;
+GtkWidget *shell_embedded_window_new (void);
+
+#endif /* __SHELL_EMBEDDED_WINDOW_H__ */