Unable to view content script references in the developer tools window

Question

When I view my extension with the developer tools, I only see the generated background file, background.js; my content script doesn't appear under the content scripts tab. Any ideas why? The relevant part of the manifest looks like this:

"content_scripts": [{
"run_at": "document_end",
"js": ["postMsg.js"],
"matches": ["https://groups.google.com/forum/*"]
}],

postMsg.js gets injected into the page, but never appears in the developer tool window, so I'm unable to debug it.

Answer 1

As long as you are on a page that matches the "Match patterns and globs" from your manifest, you will see the content script(s) under the Sources -> Content Scripts pane.
You may need to refresh (F5) the page (and/or your extension, then the page) to see it:

(Click for larger image)

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For more information on matching that cryptic number to an extension, see this answer.