Specialize SkOncePtr<T[]>.

SkOncePtr<T[]> is identical to SkOncePtr<T> except we'll default to delete[]
for cleanup.

CQ_EXTRA_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Debug-ASAN-Trybot

BUG=skia:

No public API changes.
TBR=reed@google.com

Review URL: https://codereview.chromium.org/1311893010
3 files changed