This adds some initial support for keyed element access to fast,
non-holey JSArray objects.

Also renames PropertyAccessInfoFactory to AccessInfoFactory and
PropertyAccessMode to AccessMode.

R=jarin@chromium.org
BUG=v8:4470
LOG=n

Review URL: https://codereview.chromium.org/1418213010

Cr-Commit-Position: refs/heads/master@{#31717}