| Index: ext/content.js | 
| =================================================================== | 
| --- a/ext/content.js | 
| +++ b/ext/content.js | 
| @@ -1,15 +1,17 @@ | 
| "use strict"; | 
|  | 
| // 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)) | 
| +// Note that Firefox processes API access lazily, so chrome.devtools will always | 
| +// exist but will have undefined as its value on other pages. | 
| +if (!chrome.devtools) | 
| { | 
| // Listen for messages from the background page. | 
| chrome.runtime.onMessage.addListener((message, sender, sendResponse) => | 
| { | 
| return ext.onMessage._dispatch(message, {}, sendResponse).includes(true); | 
| }); | 
| } | 
|  | 
|  |