This is required for cases where files have not changed but the
manifest logic has changed.
MozReview-Commit-ID: E46HtouILS2
--HG--
extra : rebase_source : f9d350018752f866052cf6a7a1ffd8f1d5f4ee39
This is needed because we changed the manifest format to store file hashes for
faster updating. But keeping that up to date requires the manifest to be regenerated
too often so we instead just check for changes to the actual tests that will run.
MozReview-Commit-ID: FYU5Vr6cXwd
--HG--
extra : rebase_source : c0dfd0c83d6a7c14622fbb0b98ad36816fa37a1e
James Graham