Refactor transitioning stores.

Refactor transitioning stores.

There's actually no need to have the transition as part of the HStoreNamedField instruction. In fact, it is cleaner and faster to generate a separate HStoreNamedField for the transition map. This will also help to eliminate map stores with store elimination, as well as reduce register pressure for transitioning stores on ia32.

R=hpayer@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=21383

[Benedikt Meurer, 2014-05-20 09:30:17]

PTAL

[Hannes Payer (out of office), 2014-05-20 10:50:50]

lgtm

[Benedikt Meurer, 2014-05-20 11:06:38]

Committed patchset #1 manually as r21383 (presubmit successful).