[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 b6644e849151dedffc1844d60b7a76da4d9e5115.

R=ulan@chromium.org

Committed: https://crrev.com/bb7a5eb2d89bae25f2b5ecb9515669f0ac73c111
Cr-Commit-Position: refs/heads/master@{#31836}

[Michael Starzinger, 2015-11-05 16:50:28]

As we already suspected offline, the heap verifier got mad about stale entries
in the old optimized code map that violate the marking invariant. The original
CL got reverted. This is a reland together with the fix.

Patch Set #1: Pure re-land without modifications.
Patch Set #2: The actual fix to make verifier happy.

PTAL at #2.

[ulan, 2015-11-05 17:06:27]

lgtm

[Michael Starzinger, 2015-11-05 17:24:21]

The CQ bit was checked by mstarzinger@chromium.org

[commit-bot: I haz the power, 2015-11-05 17:24:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1421903012/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1421903012/20001

[commit-bot: I haz the power, 2015-11-05 17:30:08]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-11-05 17:30:29]

Patchset 2 (id:??) landed as
https://crrev.com/bb7a5eb2d89bae25f2b5ecb9515669f0ac73c111
Cr-Commit-Position: refs/heads/master@{#31836}

[Michael Starzinger, 2015-11-05 18:49:31]

A revert of this CL (patchset #2 id:20001) has been created in
https://codereview.chromium.org/1412063012/ by mstarzinger@chromium.org.

The reason for reverting is: Causes GC-Stress failures..