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”.