`task.dependencies` is part of the internal taskgraph calculations, so it must
only refer to tasks that are being created, and not to those which already
exist. `task.task['dependencies']`, on the other hand, is what is given to
`queue.createTask` and expresses all dependencies.
MozReview-Commit-ID: GJ6JVj6JMBz
Graph morphs modify the graph after optimization, without changing its meaning.
In this case, that means adding index tasks that will insert paths into the
index beyond the relatively limited number afforded in task.routes.
MozReview-Commit-ID: AJy4exX7q2v
