Fix polymorphic keyed load handler selection for string elements

Fix polymorphic keyed load handler selection for string elements

The monomorphic case already carefully ensures that we don't try to use
a regular elements load stub on string wrapper elements. The polymorphic
path must perform an equivalent check.

BUG=chromium:594955
LOG=n
R=verwaest@chromium.org

Committed: https://crrev.com/84dd29bb3c608e60d4fcd18d0250277e034e26a7
Cr-Commit-Position: refs/heads/master@{#34807}

[Toon Verwaest, 2016-03-15 19:16:54]

LGTM for now, although it's a pretty ugly solution. We should just add support
for string wrappers.

[Jakob Kummerow, 2016-03-16 10:07:34]

The CQ bit was checked by jkummerow@chromium.org

[commit-bot: I haz the power, 2016-03-16 10:07:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1806543002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1806543002/1

[commit-bot: I haz the power, 2016-03-16 10:55:16]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-03-16 10:56:28]

Description was changed from

==========
Fix polymorphic keyed load handler selection for string elements

The monomorphic case already carefully ensures that we don't try to use
a regular elements load stub on string wrapper elements. The polymorphic
path must perform an equivalent check.

BUG=chromium:594955
LOG=n
R=verwaest@chromium.org
==========

to

==========
Fix polymorphic keyed load handler selection for string elements

The monomorphic case already carefully ensures that we don't try to use
a regular elements load stub on string wrapper elements. The polymorphic
path must perform an equivalent check.

BUG=chromium:594955
LOG=n
R=verwaest@chromium.org

Committed: https://crrev.com/84dd29bb3c608e60d4fcd18d0250277e034e26a7
Cr-Commit-Position: refs/heads/master@{#34807}
==========

[commit-bot: I haz the power, 2016-03-16 10:56:29]

Patchset 1 (id:??) landed as
https://crrev.com/84dd29bb3c608e60d4fcd18d0250277e034e26a7
Cr-Commit-Position: refs/heads/master@{#34807}