[turbofan] Add support for loading missing properties.

[turbofan] Add support for loading missing properties.

Return undefined for missing properties (or throw an exception in strong
mode). Also do a bit of code cleanup.

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

Committed: https://crrev.com/8954ea1b6f5c8d4b540a506e25d9b1ce0ea4ba22
Cr-Commit-Position: refs/heads/master@{#31700}

[Benedikt Meurer, 2015-11-02 07:17:44]

Hey Jaro,

This is the patch we're talking about offline.
Please take a look.

Thanks,
Benedikt

[Jarin, 2015-11-02 07:21:58]

lgtm

[Benedikt Meurer, 2015-11-02 07:22:11]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2015-11-02 07:22:15]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1427913003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1427913003/1

[commit-bot: I haz the power, 2015-11-02 07:35:16]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-02 07:35:34]

Patchset 1 (id:??) landed as
https://crrev.com/8954ea1b6f5c8d4b540a506e25d9b1ce0ea4ba22
Cr-Commit-Position: refs/heads/master@{#31700}