[turbofan] Fix known issue about computed property names.

[turbofan] Fix known issue about computed property names.

This fixes a corner-case where deoptimization while evaluating the
value to a __proto__ property after computed property names appeared
in an object literal, lead to environments not being in sync with
unoptimized code.

R=arv@chromium.org
TEST=mjsunit/harmony/computed-property-names-deopt

Committed: https://crrev.com/ce551f91fd18069bc6786c6c71d111fb1ebca683
Cr-Commit-Position: refs/heads/master@{#28613}

[arv (Not doing code reviews), 2015-05-22 15:10:53]

lgtm

[Michael Starzinger, 2015-05-26 08:19:02]

The CQ bit was checked by mstarzinger@chromium.org

[commit-bot: I haz the power, 2015-05-26 08:19:19]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1158443004/1

[commit-bot: I haz the power, 2015-05-26 08:45:15]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-26 08:45:28]

Patchset 1 (id:??) landed as
https://crrev.com/ce551f91fd18069bc6786c6c71d111fb1ebca683
Cr-Commit-Position: refs/heads/master@{#28613}