Using wrong virtual view id When prefetching accessibility nodes.

Using wrong virtual view id When prefetching accessibility nodes.

When getting an accessibility node info we also prefetch its predecessors,
siblings and descendants up to fifty. If a view has a node provider, i.e.
virtual descendants, and the id of the virtual descendant is not specified
we use a speacial constant to refer that the provider should create a node
for its hosting view. The bug was that we were not using the correct constant
when calling into the provider.

bug:17664111

Change-Id: I4f6b2333e1e7e3e2bb6b164c0752613417c60d16