Add missing read barriers to intern table.

Also deleted GcRoot::Assign.

(cherry picked from commit c2bda539093db61be1f4095e579f6e68db8a23f1)

(cherry picked from commit 0ba1fed9978ba2fbfe129fe62095c983e8a5391b)

Change-Id: I7158774c6a30de7e569ee7afd978fa27f667fac2
2 files changed