[serializer] Move clearing of optimized code map out of GC.

[serializer] Move clearing of optimized code map out of GC.

This avoids the need to clear optimized code maps within the GC by just
preventing entries being added in the first place, whenever a snapshot
is being constructed. The main goal here is to simplify the logic in the
already complex visitor for our shared function info objects.

R=yangguo@chromium.org

Committed: https://crrev.com/cd7c416da41d944cfa113b657d15547e78d5a877
Cr-Commit-Position: refs/heads/master@{#31852}

[Yang, 2015-11-05 18:44:38]

lgtm

[Michael Starzinger, 2015-11-05 19:39:18]

The CQ bit was checked by mstarzinger@chromium.org

[commit-bot: I haz the power, 2015-11-05 19:39:35]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1411513005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1411513005/1

[commit-bot: I haz the power, 2015-11-05 19:41:05]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-11-05 19:41:06]

Try jobs failed on following builders:
  v8_presubmit on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_presubmit/builds/7494)

[Michael Starzinger, 2015-11-06 08:48:33]

The CQ bit was checked by mstarzinger@chromium.org

[Michael Starzinger, 2015-11-06 08:48:33]

The patchset sent to the CQ was uploaded after l-g-t-m from yangguo@chromium.org
Link to the patchset: https://codereview.chromium.org/1411513005/#ps20001
(title: "Rebased.")

[commit-bot: I haz the power, 2015-11-06 08:48:43]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1411513005/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1411513005/20001

[commit-bot: I haz the power, 2015-11-06 08:56:12]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-11-06 08:56:22]

Patchset 2 (id:??) landed as
https://crrev.com/cd7c416da41d944cfa113b657d15547e78d5a877
Cr-Commit-Position: refs/heads/master@{#31852}