install userChrome.css using autoconfig instead of schell scripts (MR 2)

Firefox can run an autoconfig Javascript on startup, which can be used to
install and update userChrome.css, both when creating a new profile and
using a pre-existing one.

This removes the need for a wrapper script and related complications
(changes to $PATH, different processing for new and pre-existing
profiles...)

Co-Authored-By: Oliver Smith <ollieparanoid@postmarketos.org>

src/mobile-config-autoconfig.js

@@ -0,0 +1,33 @@
+// Copyright 2020 Arnaud Ferraris, Oliver Smith
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// This is a Firefox autoconfig file:
+// https://support.mozilla.org/en-US/kb/customizing-firefox-using-autoconfig
+
+// Import custom userChrome.css on startup or new profile creation
+const {classes: Cc, interfaces: Ci, utils: Cu} = Components;
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/FileUtils.jsm");
+
+// Create <profile>/chrome/ directory if not already present
+var chromeDir = Services.dirsvc.get("ProfD", Ci.nsIFile);
+chromeDir.append("chrome");
+if (!chromeDir.exists()) {
+  chromeDir.create(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+}
+
+// Create nsIFile objects for userChrome.css in <profile>/chrome/ and in /etc/
+var chromeFile = chromeDir.clone();
+chromeFile.append("userChrome.css");
+var defaultChrome = new FileUtils.File("/etc/mobile-config-firefox/userChrome.css");
+
+// Remove the existing userChrome.css if older than the installed one
+if (chromeFile.exists() && defaultChrome.exists() &&
+    chromeFile.lastModifiedTime < defaultChrome.lastModifiedTime) {
+  chromeFile.remove(false);
+}
+
+// Copy userChrome.css to <profile>/chrome/
+if (!chromeFile.exists()) {
+  defaultChrome.copyTo(chromeDir, "userChrome.css");
+}