Reland "Filter invalid slots out from the SlotsBuffer after marking."

Reland "Filter invalid slots out from the SlotsBuffer after marking."

> There are two reasons that could cause invalid slots appearance in SlotsBuffer:
> 1) If GC trims "tail" of an array for which it has already recorded a slots and then migrate another object to the "tail".
> 2) Tagged slot could become a double slot after migrating of an object to another map with "shifted" fields (for example as a result of generalizing immutable data property to a data field).

> This CL also adds useful machinery that helps triggering incremental write barriers.

> BUG=chromium:454297
> LOG=Y

NOTRY=true

Committed: https://crrev.com/f86aadd1d45c756467dff8e08a055b462d7a060b
Cr-Commit-Position: refs/heads/master@{#27433}

[ulan, 2015-03-25 08:50:24]

ulan@chromium.org changed reviewers:
+ ishell@chromium.org, machenbach@chromium.org

[ulan, 2015-03-25 08:50:25]

PTAL. The original CL: https://codereview.chromium.org/1010363005

[Michael Achenbach, 2015-03-25 08:52:35]

lgtm

[Michael Achenbach, 2015-03-25 08:52:38]

The CQ bit was checked by machenbach@chromium.org

[commit-bot: I haz the power, 2015-03-25 08:52:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1032833002/2

[commit-bot: I haz the power, 2015-03-25 08:52:56]

Committed patchset #2 (id:2)

[commit-bot: I haz the power, 2015-03-25 08:53:05]

Patchset 2 (id:??) landed as
https://crrev.com/f86aadd1d45c756467dff8e08a055b462d7a060b
Cr-Commit-Position: refs/heads/master@{#27433}

[Igor Sheludko, 2015-03-27 06:50:38]

A revert of this CL (patchset #2 id:2) has been created in
https://codereview.chromium.org/1041593002/ by ishell@chromium.org.

The reason for reverting is: Reverting risky GC changes that block v8 roll..