Service worker throwing an net::ERR_FILE_EXISTS error?

I'm seeing the same issue. It can safely be ignored.

This bug tracks removing the noise from Chrome: https://code.google.com/p/chromium/issues/detail?id=541797

It should be live starting with Chrome 50.

From thread:

Improve error code for service worker bailing due to no update found

ServiceWorkerWriteToCacheJob is the URLRequestJob responsible for fetching and writing the updated script. It fails with network error when it wants to abort the update because the new script is the same as the old one.

Currently that results in ERR_FAILED errors appearing in the DevTools console and netlog, which is confusing and hard to debug because that error also occurs for actual network errors. This patch changes the error to FILE_EXISTS, so it's more clear why the job "failed".