Megamorphic KeyedLoadIC needs special handling for vector ics.

Megamorphic KeyedLoadIC needs special handling for vector ics.

When --vector-ics is true, we still tail-call to the hand-written
megamorphic KeyedLoadIC (formerly "generic"). Now that this code uses
the megamorphic cache, it needs to deal properly with the vector and
slot registers. Achieve this with a sentinel vectors/slot combo.

R=dcarney@chromium.org
BUG=

Committed: https://crrev.com/16843e239d95f5e8eaaa06d2a0a6e371298fe11f
Cr-Commit-Position: refs/heads/master@{#26381}

[mvstanton, 2015-02-02 13:09:27]

Hi Dan, here is the change to restore --vector-ics functionality. Thanks for the
look!
--Michael

[dcarney, 2015-02-02 13:12:14]

lgtm, assuming no registers are trashed before getting to that point

[mvstanton, 2015-02-02 13:41:06]

The CQ bit was checked by mvstanton@chromium.org

[commit-bot: I haz the power, 2015-02-02 13:42:02]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/892173002/1

[commit-bot: I haz the power, 2015-02-02 13:55:07]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-02 13:55:33]

Patchset 1 (id:??) landed as
https://crrev.com/16843e239d95f5e8eaaa06d2a0a6e371298fe11f
Cr-Commit-Position: refs/heads/master@{#26381}