Issue 4139 - Don't save element hiding filters on disk

lib/elemHideStylesheet.js

Index: lib/elemHideStylesheet.js
===================================================================
new file mode 100644
--- /dev/null
+++ b/lib/elemHideStylesheet.js
@@ -0,0 +1,104 @@
+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-2016 Eyeo GmbH
+ *
+ * Adblock Plus is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * Adblock Plus 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+"use strict";
+
+let {port} = require("messaging");
+let {ElemHide} = require("elemHide");
+let {FilterNotifier} = require("filterNotifier");
+let {Prefs} = require("prefs");
+let {Utils} = require("utils");
+
+/**
+ * Indicates whether the element hiding stylesheet is currently applied.
+ * @type Boolean
+ */
+let applied = false;
+
+/**
+ * Stylesheet URL to be registered
+ * @type nsIURI
+ */
+let styleURL = Utils.makeURI("about:abp-elemhidehit?css");
+
+function init()
+{
+  port.on("getSelectors", () => ElemHide.getSelectors());
+
+  apply();
+  onShutdown.add(unapply);
+
+  Prefs.addListener(function(name)
+  {
+    if (name == "enabled")
+      apply();
+  });
+
+  FilterNotifier.on("elemhideupdate", onUpdate);
+}
+
+function onUpdate()
+{
+  // Call apply() asynchronously and protect against reentrance - multiple
+  // change events shouldn't result in multiple calls.
+  if (onUpdate.inProgress)
+    return;
+
+  onUpdate.inProgress = true;
+  Utils.runAsync(() =>
+  {
+    onUpdate.inProgress = false;
+    apply();
+  });
+}
+
+function apply()
+{
+  unapply();
+
+  try
+  {
+    Utils.styleService.loadAndRegisterSheet(styleURL,
+        Ci.nsIStyleSheetService.USER_SHEET);
+    applied = true;
+  }
+  catch (e)
+  {
+    Cu.reportError(e);
+  }
+}
+
+function unapply()
+{
+  if (applied)
+  {
+    try
+    {
+      Utils.styleService.unregisterSheet(styleURL,
+          Ci.nsIStyleSheetService.USER_SHEET);
+    }
+    catch (e)
+    {
+      Cu.reportError(e);
+    }
+    applied = false;
+  }
+}
+
+// Send dummy message before initializing, this delay makes sure that the child
+// modules are loaded and our protocol handler registered.
+port.emitWithResponse("ping").then(init);