This makes clear that some benchmarks where Array.from is used to
clone the array are very fast because the array is COW, and the
added benchmarks for non-COW arrays are not as fast. COW-ness does
not affect benchmarks where Array.from is called with a callback
function.

Change-Id: Ie9dd5507df5dd7501ac955dba4d3682c4a54548e
Reviewed-on: https://chromium-review.googlesource.com/c/1314333Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Hai Dang <dhai@google.com>
Cr-Commit-Position: refs/heads/master@{#57208}