Background Fetch currently is not supported WebView and so will not function correctly.
Before we ship, we should either:
a) Enable support for it directly.
b) Explicitly disable it so that WebView does not act if it exists with fetches mysteriously failing.
Bug filed as per comments here:
https://chromium-review.googlesource.com/c/chromium/src/+/647751/18
Comment 1 by delph...@chromium.org
, Sep 18 2017