Where the arguments have already been inlined, we can replace these
calls with a direct call. We have to make sure that the iteration over
the arguments is not observable.

Also factor out the large chunk of logic shared with
ReduceJSConstructWithSpread.

BUG=v8:5932

Change-Id: I6c4fac670028fbd8ca82c4474d4392231573bc49
Reviewed-on: https://chromium-review.googlesource.com/439329Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43039}