shell-util: Add a helper method for saving files from HTTP

Unfortunately, gjs cannot handle binary C strings directly from
gobject-introspection. Add a simple workaround method in C to help
us save random files from the web.

https://bugzilla.gnome.org/show_bug.cgi?id=653989

src/shell-util.c

@@ -560,6 +560,29 @@ shell_get_event_state (ClutterEvent *event)
   return state & CLUTTER_MODIFIER_MASK;
 }
 
+/**
+ * shell_write_soup_message_to_stream:
+ * @stream: a #GOutputStream
+ * @message: a #SoupMessage
+ * @error: location to store GError
+ *
+ * Write a string to a GOutputStream as binary data. This is a
+ * workaround for the lack of proper binary strings in GJS.
+ */
+void
+shell_write_soup_message_to_stream (GOutputStream *stream,
+                                    SoupMessage   *message,
+                                    GError       **error)
+{
+  SoupMessageBody *body;
+
+  body = message->response_body;
+
+  g_output_stream_write_all (stream,
+                             body->data, body->length,
+                             NULL, NULL, error);
+}
+
 /**
  * shell_write_string_to_stream:
  * @stream: a #GOutputStream