Correct Preconditions.checkNotNull usage.

Reference to check should be first parameter. Since Preconditions
doesn't have the right overload using Objects.requireNonNull, transition
to which was already planned.

Bug: 146340409

Test: Treehugger
Change-Id: I77b8c1f247c2f6e9abdbfe3bc627be04bd4d407b
2 files changed