[heap] Separate out optimized code map processing.

[heap] Separate out optimized code map processing.

This separates the post-processing step for optimized code maps out of
the CodeFlusher. It uses the complete SharedFunctionInfo::Iterator to
visit all candidates instead of gathering candidates during marking.

Gathering candidates during marking no longer makes sense, now that the
majority of SharedFunctionInfo objects will hold such an optimized code
map. Also it reduces complexity of the implementation. Also conflating
this mechanism with "code flushing" was confusing.

This reverts commit 7f1fb29faa4fe8ebd39d69fdfcdd1f2a3ac09579.

R=ulan@chromium.org

Committed: https://crrev.com/087513d6d4a710f7360d2a71abb4e324168ad571
Cr-Commit-Position: refs/heads/master@{#31876}

[Michael Starzinger, 2015-11-06 09:53:30]

As discussed offline, there is a race between the mutator adding a new entry and
the GC flushing optimized code maps Smi(0). The workaround we discussed is to
just give up on adding the entry in that case. The original CL got reverted.
This is a reland together with the workaround.

Patch Set #1: Pure re-land without modifications.
Patch Set #2: The actual workaround for the race.

PTAL at #2.

[ulan, 2015-11-06 14:37:33]

lgtm

[Michael Starzinger, 2015-11-09 10:49:52]

The CQ bit was checked by mstarzinger@chromium.org

[Michael Starzinger, 2015-11-09 10:49:52]

The patchset sent to the CQ was uploaded after l-g-t-m from ulan@chromium.org
Link to the patchset: https://codereview.chromium.org/1418453008/#ps40001
(title: "Rebased.")

[commit-bot: I haz the power, 2015-11-09 10:50:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1418453008/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1418453008/40001

[commit-bot: I haz the power, 2015-11-09 11:05:25]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-11-09 11:06:00]

Patchset 3 (id:??) landed as
https://crrev.com/087513d6d4a710f7360d2a71abb4e324168ad571
Cr-Commit-Position: refs/heads/master@{#31876}