Add a helper to handle captive portal logins

Add a small DBus-activated GtkApplication that embeds a WebKitWebView
and implements some minimal logic to see if the login succeeds.
It will try to connect to a custom NM-provided url (the portal login
page), if one exists, or to www.gnome.org in the normal case of
a portal doing redirect.

https://bugzilla.gnome.org/show_bug.cgi?id=704416

src/Makefile.am

@@ -199,6 +199,21 @@ nodist_gnome_shell_extension_prefs_SOURCES = \
 gnome_shell_extension_prefs_CPPFLAGS = $(gnome_shell_cflags)
 gnome_shell_extension_prefs_LDADD = libgnome-shell-js.la $(GNOME_SHELL_LIBS)
 
+if HAVE_NETWORKMANAGER
+
+libexec_PROGRAMS += gnome-shell-portal-helper
+gnome_shell_portal_helper_SOURCES = \
+	gnome-shell-portal-helper.c \
+	$(NULL)
+nodist_gnome_shell_portal_helper_SOURCES = \
+	$(top_builddir)/js/js-resources.c		\
+	$(top_builddir)/js/js-resources.h		\
+	$(NULL)
+gnome_shell_portal_helper_CPPFLAGS = $(gnome_shell_cflags)
+gnome_shell_portal_helper_LDADD = libgnome-shell-js.la $(GNOME_SHELL_LIBS)
+
+endif
+
 ########################################
 
 libgnome_shell_js_la_SOURCES =		\

src/gnome-shell-portal-helper.c

@@ -0,0 +1,52 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
+
+#include "config.h"
+
+#include <girepository.h>
+#include <gjs/gjs.h>
+#include <glib/gi18n.h>
+
+int
+main (int argc, char *argv[])
+{
+  const char *search_path[] = { "resource:///org/gnome/shell", NULL };
+  GError *error = NULL;
+  GjsContext *context;
+  int status;
+
+  bindtextdomain (GETTEXT_PACKAGE, LOCALEDIR);
+  bind_textdomain_codeset (GETTEXT_PACKAGE, "UTF-8");
+  textdomain (GETTEXT_PACKAGE);
+
+  g_irepository_prepend_search_path (GNOME_SHELL_PKGLIBDIR);
+
+  context = g_object_new (GJS_TYPE_CONTEXT,
+                          "search-path", search_path,
+                          NULL);
+
+  if (!gjs_context_define_string_array(context, "ARGV",
+                                       argc, (const char**)argv,
+                                       &error))
+    {
+      g_message("Failed to define ARGV: %s", error->message);
+      g_error_free (error);
+
+      return 1;
+    }
+
+
+  if (!gjs_context_eval (context,
+                         "const Main = imports.portalHelper.main; Main.main(ARGV);",
+                         -1,
+                         "<main>",
+                         &status,
+                         &error))
+    {
+      g_message ("Execution of main.js threw exception: %s", error->message);
+      g_error_free (error);
+
+      return status;
+    }
+
+  return 0;
+}