Prevent the page from seeing "j" presses

gistfile1.diff

https://github.com/Mardak/restartless/blob/watchWindows/bootstrap.js
diff --git a/bootstrap.js b/bootstrap.js
index d9f353c..d2a3cd8 100644
--- a/bootstrap.js
+++ b/bootstrap.js
@@ -150,7 +150,17 @@ function unload(callback, container) {
 /**
  * Handle the add-on being activated on install/enable
  */
-function startup(data, reason) {}
+function startup(data, reason) {
+  watchWindows(function(window) {
+    let noJ = function(event) {
+      if (String.fromCharCode(event.charCode) == "j")
+        event.stopPropagation();
+    };
+
+    window.gBrowser.addEventListener("keypress", noJ, true);
+    unload(function() window.gBrowser.removeEventListener("keypress", noJ, true));
+  });
+}
 
 /**
  * Handle the add-on being deactivated on uninstall/disable