This unifies the search for a potential {IfException} projection with
the existing predicate on {NodeProperties} used by the rest of the
system. Also contains a related drive-by change to graph builders. This
is in preparation of eliding {IfSuccess} projections when possible.

R=jarin@chromium.org

Change-Id: I8ba0ae9e9fdb69a77bce01578200ceea434535f7
Reviewed-on: https://chromium-review.googlesource.com/448039Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43540}