This ensures that each repository's "npm test" command is fully
independent of wherever it might be in the filesystem.
Bug: T206485
Change-Id: I7f96f21d586e198abbeb965471dec620abecd845
Long-term todo:
* Performance will be poor on large pages due
to using a auto-height textarea which CodeMirror
doesn't optimise.
Change-Id: I16598fcdbeee51e6fae88376ec81f1c8552b383d