Fix forging of object's identity hashes.

Fix forging of object's identity hashes.

Do not do standard property lookup on hidden properties object as it might
reach Object.prototype which can be altered to forge identity hashes.
Instead do only local lookup.

Committed: http://code.google.com/p/v8/source/detail?r=6728

[antonm, 2011-02-09 19:15:25]

Mads,

a review for you.

[Mads Ager (chromium), 2011-02-10 10:14:23]

LGTM