In Array.prototype.map, we have to store the map result in an output array.
If we know we are storing objects, or special objects like boolean, rather
than a number, then we can reduce the amount of checks we have to do to
transition the output array to the appropriate ElementsKind.

Likewise, if we know we've got floating point values, we can specialize 
appropriately to a double array.

Bug: v8:6896
Change-Id: I375daf604562b53638ea749945c1a4c907e33547
Reviewed-on: https://chromium-review.googlesource.com/711845
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48579}