This was internal to CategoryTree JS code and only needed on very
few pages. Export it as part of the module that needs it, instead.
Given this is computed and not a plain config var, use callback
to generate the value.
Bug: T219342
Change-Id: I790a98128b0a3317e27ac0d5fda08d48aeb640dc
This ensures that each repository's "npm test" command is fully
independent of wherever it might be in the filesystem.
Bug: T206485
Change-Id: I1cbbf2644fed413b77cd7203450151c3e315c815
