At the moment, when checking which requests should be sent to the client, we are checking if the window the request was emitted from belongs to the "target window tree" (see https://searchfox.org/mozilla-central/rev/1761c710b035d7dc8892dfa8e56589b4e095221f/devtools/server/actors/network-monitor/network-observer.js#109-120 for example)

With Bug 1685500, we'll have targets for each document, so we can do an exact match on the window instead, as requests from iframes will be included from the iframes targets.

When we create targets for every frame, we need to tighten our different filters
so requests/resources are duplicated (we would get them from both the top-level
target as well as from their iframe).

https://hg.mozilla.org/mozilla-central/rev/af80802b2175