ART: DCHECK still too strong for String NewInstance

Even though the presence of a irreducible loop phi is the reason why
String.<init> may see its first input not being the NewInstance, it
may see a different phi from the same cycle. We have to relax the
corresponding DCHECK.

Bug: 26676472
Change-Id: Iba6fffa74833c57aad8aa07dc382ff6b93838de1
3 files changed