Comment 20 for bug 1232575

Perfect. I found the fix; it was most likely a syntax/parsing error in extension.json which then probably caused the entire file to not be read.

Instead of the following lines:
+ "name": "isChromelessWindow",
+ "type": "function",
+ "unprivileged": true,
+ "description": "Checks is a given extension runs part of a chromeless window.",

use the following lines:
+ "name": "isChromelessWindow",
+ "nocompile": true,
+ "nodoc": true,
+ "type": "function",
+ "description": "Checks is a given extension runs part of a chromeless window.",

We don't have docs in the docs folder, and I'm not sure what nocompile does.