Yes, I looked at the diff. A diff like the author probably had been looking through all day. You've never missed a line? They probably thought it was just whitespace changes or, you know, just missed it entirely.

If we're going to claim this is deliberate, then the same accusation can be levelled at every security bug ever introduce in an edit. This is not evidence, it's just trolling.

Not really, most editors support the ability to duplicate a line using CMD+D, including AppCode by JetBrains. In my case, using Colemak, S is mapped to D, and so if I'm in the wrong keyboard layout, I'll go to save and end up duplicating a line, then saving by hitting the right key. If I'm not careful, I'll have saved a duplicate line without noticing.

Similarly, given how the rest of the changes seemed to be attempts to rename and clean up the API, I expect that it was a junior intern cleaning up code as a whole. It would be more interesting to see the history of the commits, but that's not public (that I know of). It does highlight how we get that data with Google's Android, even though the development and release process is basically the same.

Why does the fact that it's the only change in that hunk make it suspicious?