Slow parsing of long unsupported URL on opening new URL

[Self-Perfection]

This is a continuation of #125
Less severe but probably still worth noting.

On very long view-source: URLs OpenSwitchMaps blocked addons execution for dozens of seconds. So I wondered if the same applies to long https? URLs, that are still handled by 1.5.4.

So here is my test: I recorded profile for opening 11 KiB URL. OpenSwitchMaps consumed 1s of CPU time: https://share.firefox.dev/4arDszp

I made URL for test this way:

echo https://ipfs.io/ipfs/QmYwAPJzv5CZsnA625s3Xf2nemtYgPpHdWEz79ojWnPbdG/readme?$(printf '%s&' map=10/{1..24}.123/{1..23}.456)endofparams

It is definitely is not supported site so should not trigger OpenSwitchMaps.

I admit that such long URLs are extremely rare. Yet according to my browsing history login URLs about 1.5 KiB length are quite common. So I think even 1.5.4 release makes Firefox hiccup sometimes on navigation.