Works great but sometimes, it throws error "NOT_FOUND: Requested entity was not found." when I click on View Source.

Not Working.
When i press view source I got error:
NOT_FOUND: Requested entity was not found.
[type.googleapis.com/google.rpc.LocalizedMessage]
locale: "en-US"
message: "Object is not found"
[type.googleapis.com/google.rpc.RequestInfo]
request_id: "514a9748a6854aa3bdc49cf96aff2048"

I tried it for this page (https://developer.android.com/reference/android/support/v7/app/AppCompatActivity)

Sometimes "View source" doesn't show up at all.
windows 10, FireFox 68.0.2 (64-bit).

Currently broken. View source button is at the bottom of the page. Not below the class name as on screenshot.

One of my favourite firefox plugins: it makes it so much more convenient to visit android documentation.

This makes it so easy to get to the specific dev doc I'm looking for.