Issue 3880 - Improve behavior of Safari content blocker option

options.js

Index: options.js
===================================================================
--- a/options.js
+++ b/options.js
@@ -718,7 +718,14 @@
     function(features)
     {
       hidePref("show_devtools_panel", !features.devToolsPanel);
-      hidePref("safari_contentblocker", !features.safariContentBlocker);
+
+      // Only show option to switch between Safari Content Blockers
+      // and event based blocking if both are available.
+      hidePref("safari_contentblocker", !(
+        features.safariContentBlocker &&
+        "canLoad" in safari.self.tab &&
+        "onbeforeload" in Element.prototype
+      ));
     });
 
     var filterTextbox = document.querySelector("#custom-filters-add input");
@@ -1080,13 +1087,18 @@
     switch (message.type)
     {
       case "app.respond":
-        if (message.action == "addSubscription")
+        switch (message.action)
         {
-          var subscription = message.args[0];
-          var dialog = E("dialog-content-predefined");
-          dialog.querySelector("h3").textContent = subscription.title || "";
-          dialog.querySelector(".url").textContent = subscription.url;
-          openDialog("predefined");
+          case "addSubscription":
+            var subscription = message.args[0];
+            var dialog = E("dialog-content-predefined");
+            dialog.querySelector("h3").textContent = subscription.title || "";
+            dialog.querySelector(".url").textContent = subscription.url;
+            openDialog("predefined");
+            break;
+          case "safariRestartRequired":
+            E("restart-safari").setAttribute("aria-hidden", !message.args[0]);
+            break;
         }
         break;
       case "filters.respond":
@@ -1104,7 +1116,7 @@
   ext.backgroundPage.sendMessage(
   {
     type: "app.listen",
-    filter: ["addSubscription"]
+    filter: ["addSubscription", "safariRestartRequired"]
   });
   ext.backgroundPage.sendMessage(
   {