https://download.kde.org/stable/heaptrack/1.0.0/src/ Heaptrack has a stable release and this should be reflected in the ebuilds that are offered. Someone might hesitate to unmask and use live heaptrack but it already has a stable version to use. I think that dev-util/heaptrack-1.0.0 should be provided.
*** This bug has been marked as a duplicate of bug 611400 ***