6908208: UseCompressedOops: array_size() returns incorrect size for MAX_INT object array following 6906727
Summary: In array_size() cast to an unsigned to avoid overflow of intermediate value.
Reviewed-by: kvn, tonyp, jmasa, jcoomes, coleenp
6904967: G1: some CollectionUsageThreshold tests fail
Summary: ensure that max and committed are non-zero (currently: at least as large as the region size).
Reviewed-by: iveresov, mchung