This fixes missing incremental write barrier issue when double fields unboxing is enabled.

This fixes missing incremental write barrier issue when double fields unboxing is enabled.

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

BUG=chromium:469146
LOG=Y

Committed: https://crrev.com/9d2d8a9c8d87c35fbc5aacc16f87f2846a2896d4
Cr-Commit-Position: refs/heads/master@{#27503}

[Igor Sheludko, 2015-03-27 20:28:27]

Patchset #1 (id:1) has been deleted

[Igor Sheludko, 2015-03-27 20:30:32]

ishell@chromium.org changed reviewers:
+ hpayer@chromium.org

[Igor Sheludko, 2015-03-27 20:30:32]

PTAL

[Hannes Payer (out of office), 2015-03-27 21:29:04]

lgtm

[Hannes Payer (out of office), 2015-03-27 21:29:08]

The CQ bit was checked by hpayer@chromium.org

[commit-bot: I haz the power, 2015-03-27 21:29:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1039733003/20001

[commit-bot: I haz the power, 2015-03-27 21:55:32]

Committed patchset #1 (id:20001)

[commit-bot: I haz the power, 2015-03-27 21:55:48]

Patchset 1 (id:??) landed as
https://crrev.com/9d2d8a9c8d87c35fbc5aacc16f87f2846a2896d4
Cr-Commit-Position: refs/heads/master@{#27503}