This is stage 1 for implementing bug 1523367 and for our current purposes probably quite sufficient for desktop and single-hosted test environments.

The idea is to have a pref like this:
network.socket.forcePort = "443,8443-8999=8081;80,808=8080"

All requests to default 443 and any port in range 8443 to 8999 will actually open to port 8081
All requests to default 80 and non-default 808 will go to port 8080.

When cross-used with network.dns.forceResolve we have a near-identical support for remapping as Chrome has, except that we can't map individual hosts, this pref applies to all but localhost and 127.0.0.1.

I'll leave bug 1523367 open for now if we need that.

Backed out changeset 84f69fc66690 (bug 1596799) for Browser-chrome failures in /builds/worker/workspace/build/src/netwerk/base/nsSocketTransportService2.cpp. CLOSED TREE

Log:
https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=285087531&repo=autoland&lineNumber=11397

https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=285090766&repo=autoland&lineNumber=6182

Push with failures:
https://treeherder.mozilla.org/#/jobs?repo=autoland&group_state=expanded&revision=84f69fc666905797db06346a98b23eb5e43cfe55

Backout:
https://hg.mozilla.org/integration/autoland/rev/633db53d4ade65575696272d544282b57f1a8d9c

Updated, rebased, this time with try pushes:
https://treeherder.mozilla.org/#/jobs?repo=try&revision=49187e6329d083573b49a31375cfa76d422f1299
https://treeherder.mozilla.org/#/jobs?repo=try&revision=8f64eb810d5bc3fa5eb732e58e8ee0ad72e2ac91

https://hg.mozilla.org/mozilla-central/rev/eea4cd13b292