Test component type for errors too.

With regression test.

Rationale:
Moved erroneous check in convenience method, so we
put all the same logic in one place. When testing
for erroneous T[], check both the array type
as well at the component type T for errors
(it is possible T[] is not marked erroneous
even though T is eventually).

BUG=28358598

Change-Id: I11339a976dc83e0493a99e6bb97f3a058ca3f796