Removing Android OS. This bug affects all platforms

The banner checking is triggered when AppBannerManager::DidFinishLoad is called. If the site injects its manifest after the load event is dispatched, then there's not really anything we can do. It's not feasible to poll and wait until a manifest link appears.

If it really wants to inject a manifest tag via Javascript, it should do in a script section in the head or something like that so it happens before the banner pipeline starts.

One option would be to plumb ManifestManager::DidChangeManifest() on the renderer side to Chrome. We do something similar for the page title and for favicons. I am unsure whether it is worth it for the manifest URL.

I'm not particularly enamoured of adding more IPC to account for this since all of the usual advice is to use static link tags for the manifest. WontFixing for now; we can reconsider this in future if a huge trend towards late injection of manifests occurs.