A std::unique_ptr of array type uses the "delete[]" operator to delete
the memory, hence we should use "new[]" to allocate it.
I sometimes get this reported locally, even though I have
"alloc_dealloc_mismatch=0" in ASAN_OPTIONS. So why not just fix it.

R=marja@chromium.org

Bug: v8:7754
Change-Id: I026287a0e0ee4b9560c4fc7333267e738392b13f
Reviewed-on: https://chromium-review.googlesource.com/1057230Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53154}