Bug 1402142 - Expand taskgraph sparse checkout to support moz.build evaluation; r=glandium

Some moz.build files need to import in-tree Python modules in order to
parse test manifests. While bug 1402010 details a better solution
to remove this requirement, the easy fix is to expand the sparse
checkout to include the missing files.

MozReview-Commit-ID: FSx6u6r2XfE

--HG--
extra : rebase_source : 6e406dd76b4f78521cbbdc40110d0610c75e2b08
extra : amend_source : f68341a14f50c8ff6e7b62214fa455b75eabe908

build/sparse-profiles/taskgraph

@@ -7,6 +7,10 @@ path:browser/locales/all-locales
 # Lots of random files in here are read. Just pull in the whole thing.
 path:build/
 
+# TODO remove once bug 1402010 is resolved and test manifests aren't
+# processed in Files() reading mode in moz.build files.
+path:layout/tools/reftest/
+
 # This file is read as part of validating the taskgraph.
 path:mobile/locales/l10n-changesets.json