Issue 5386 - Ignore messages from content scripts in devtools panel

ext/content.js

Index: ext/content.js
===================================================================
--- a/ext/content.js
+++ b/ext/content.js
@@ -1,14 +1,23 @@
 "use strict";
 
-chrome.runtime.onMessage.addListener((message, sender, sendResponse) =>
+// Firefox 55 erroneously sends messages from the content script to the
+// devtools panel:
+// https://bugzilla.mozilla.org/show_bug.cgi?id=1383310
+// As a workaround, listen for messages only if this isn't the devtools panel.
+if (!("devtools" in chrome))
 {
-  return ext.onMessage._dispatch(message, {}, sendResponse).indexOf(true) != -1;
-});
+  // Listen for messages from the background page.
+  chrome.runtime.onMessage.addListener((message, sender, sendResponse) =>
+  {
+    return ext.onMessage._dispatch(message, {}, sendResponse).indexOf(true) !=

[Sebastian Noack, 2017/08/16 10:15:00]

While changing this code anyway, you might want to replace `.indexOf(true) !=
-1` with `.contains(true)`. Then you also wouldn't need to wrap this line.

[Manish Jethani, 2017/08/16 10:30:36]

I'm assuming you meant `.includes(true)`

Done.

[Sebastian Noack, 2017/08/16 10:34:56]

Sure, that is what I meant, sorry.

+           -1;
+  });
+}
 
 (function()
 {
   let port = null;
 
   ext.onExtensionUnloaded = {
     addListener(listener)
     {