This works only for platforms supporting the return of
Promise by network listeners, i.e. only Firefox at this
point.
When filter lists are reloaded[1], there is a small
time window in which some network requests which should
have normally been blocked are not being blocked
because the static network filtering engine may not
have yet loaded all the filters in memory
This is now addressed by suspending the network request
handler when filter lists are reloaded -- again, this
works only on supported platforms.
[1] Examples: when a filter list update session
completes; when user filters change, when
adding/removing filter lists.
Related issue:
- https://github.com/uBlockOrigin/uBlock-issues/issues/407
Both flavors will be stitched together into a single
`vapi-qebrequest.js` file.
The decision of which flavor to use will be made at runtime,
according to the browser environment.
