Not sure what you mean with "PNACL Chrome FileSystem API"? The only thing that should be broken by my change is the StreamToFile flag when doing a URLRequest. Which according to our statistics is a feature that is used in a vanishingly tiny number of page loads. And if I'm understanding things correctly (I'm unfortunately not a PPAPI expert) you should still be able to get very similar behavior by streaming the data from a url request to a file in the sandboxed filesystem manually.

Unfortunately it sounds like this is not going to be fixed.   

Not having StreamToFile supported breaks my app that makes use of the documented function.   I will have to rewrite my code, QA it and deploy the change to all of our websites.   

In the future is there a way to know what Chrome API features are not popular and are going to be removed?

I'm really sorry about the lack of communication around this change. We should of course have tried to reach out to developers to announce this deprecation/removal. But yeah, it's unlikely to change at this point, especially since ultimately all of PNaCl is going to get deprecated/removed anyway (i.e. https://developer.chrome.com/native-client/migration#p-nacl-deprecation-announcements, although that says Q1 2018, which obviously didn't happen).

(and even though the table on that migration page claims there is no open web replacement for StreamToFile, that isn't technically true. XHR to a blob does exactly the same as what StreamToFile used to do).

I'm not sure if there is some general way to be informed about PPAPI/PNACL changes, although I also don't think there are many changes in that area, given it's all deprecated/going away anyway (but again, I don't usually work in this area, so I might be wrong). In general though chromestatus.com is where we track removal and addition of new web platform features in chrome. But I didn't create an entry for this change there, even though I probably should have.

I don't think this is Servicification related. removing label.

Assigning to @mek@chromium.org  for further action on this and not adding any blocker as this seems to be an intended change.

Thanks.!

> Does this work in other browsers? Yes
No other browser supports Native Client, this is not an interoperability issue.

Marking this WontFix. I realize this is unfortunate, but given that PNaCl is deprecated anyway, and the fact that workarounds exists I don't see much reason to change course and try to bring back the StreamToFile API that was intentionally removed. Usage numbers are extremely low as well (https://www.chromestatus.com/metrics/feature/timeline/popularity/2396).