Work around ICE bugs with MIPS GCC and O1.

Also, work around GCC warning bugs where array accesses with explicit
bounds checks are flagged as being out-of-bounds. Significantly, clean-up
the HandleScope so the array accesses don't appear out-of-bounds at compile
time.

Change-Id: I5d66567559cc1f97cd0aa02c0df8575ebadbfe3d