Right now inspectNode and inspectA11Y assume a single walker front/actor when resolving a node front from a content DOM reference. This needs to be updated to take into account multiple walkers for various remote frames.

Julian, I have a patch however it still does not seem to work as is... I test it on https://developer.mozilla.org/en-US/docs/Web/HTML/Element/iframe where I try to inspect a zoom in/zoom out button within the embedded map iframe which does not seem to work. getNodeActorFromContentDomReference returns null for all walkers...

The issue seems to be that the ContentDOMReference object for given walkers is not in the same content process as the one that was used to set targetIdentifier in the context menu..

Backed out changeset d3dc60cc5291 (bug 1610562) for devtools failures in browser_inspector_inspect_node_contextmenu.js

Push that started the failures: https://treeherder.mozilla.org/#/jobs?repo=autoland&resultStatus=pending%2Crunning%2Csuccess%2Csuperseded%2Ctestfailed%2Cbusted%2Cexception%2Crunnable&searchStr=linux%2C18.04%2Cx64%2Cdebug%2Cmochitests%2Ctest-linux1804-64%2Fdebug-mochitest-devtools-chrome-e10s-7%2Cm%28dt7%29&fromchange=1258487ed8ced1f7bb2a77a6be0c0f5ee6ecd6d9&tochange=8e70567acc3b890065d51a50056be99a5176c819&selectedJob=286406012

Failure log: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=286406012&repo=autoland&lineNumber=7513

Backout: https://hg.mozilla.org/integration/autoland/rev/e15adad7c221b40a0a06b805d4cbefab8f358f8b

Looks like there are unresolved dependencies for this landing , unless we land it under a pref. Will hold off for a little while.

https://hg.mozilla.org/mozilla-central/rev/eadaf41bc8dc