Get rid of HStoreNamedField::SkipWriteBarrier().

Get rid of HStoreNamedField::SkipWriteBarrier().

The write barrier elimination does the right thing now, so
we can get rid of this hack.

R=mvstanton@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=21384

[Benedikt Meurer, 2014-05-20 11:14:18]

Hey Michael,
Here's the SkipWriteBarrier() goodness we're talking about. :-)
PTAL
-- Benedikt

[mvstanton, 2014-05-20 11:18:37]

I like adding the todo in my name ;^).
lgtm.

[Benedikt Meurer, 2014-05-20 11:25:55]

Committed patchset #1 manually as r21384 (presubmit successful).