[turbofan] Support preserving of optimized code maps over GCs.

[turbofan] Support preserving of optimized code maps over GCs.

This extends the existing support for --noflush-optimized-code-cache
mechanism to the newly added context-independent code entry in the
optimized code map. Note that this machanism is still off by default.

R=hpayer@chromium.org

Committed: https://crrev.com/7a615a4596cc9e255d1e285825c79f7ca79eb8c0
Cr-Commit-Position: refs/heads/master@{#29415}

[Hannes Payer (out of office), 2015-07-01 12:26:54]

lgtm

[Michael Starzinger, 2015-07-01 12:27:55]

The CQ bit was checked by mstarzinger@chromium.org

[commit-bot: I haz the power, 2015-07-01 12:28:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1220883002/20001

[commit-bot: I haz the power, 2015-07-01 12:29:32]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-07-01 12:29:51]

Patchset 2 (id:??) landed as
https://crrev.com/7a615a4596cc9e255d1e285825c79f7ca79eb8c0
Cr-Commit-Position: refs/heads/master@{#29415}