parseJsonl() was a private function inside json-viewer.mjs, a page
entry-point that renders React and reads the JSONView content global at
load time, so nothing else could import it. JsonlLineError lived in
jsonview/, and the JSON Lines content types were spelled out inline in
the sniffer and twice in fixSave().
The Netmonitor needs all three (bug 2059673), so move them to
devtools/client/shared/jsonl-utils.mjs and have jsonview import from
there. JsonlLineError also gains a Symbol.for() brand and an isInstance()
helper, so consumers loading the module through a different global still
recognise its instances.
The only behaviour change: a line which fails to parse is reparsed
preceded by the blank lines it comes after in the document, so that its
error message points at the line in the document rather than at line 1.
Differential Revision: https://phabricator.services.mozilla.com/D320918
Benoit Goupilleau
6470e8361a