[heap] Remove raw unchecked root set accessors.

[heap] Remove raw unchecked root set accessors.

R=hpayer@chromium.org
BUG=v8:1490
LOG=n

Committed: https://crrev.com/e276f5d89e2460dee1d5d925635622fbdb8580c2
Cr-Commit-Position: refs/heads/master@{#30412}

[Hannes Payer (out of office), 2015-08-27 13:23:18]

The CQ bit was checked by hpayer@chromium.org

[commit-bot: I haz the power, 2015-08-27 13:23:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1305163007/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1305163007/20001

[commit-bot: I haz the power, 2015-08-27 13:23:27]

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

[commit-bot: I haz the power, 2015-08-27 13:23:27]

No L-G-T-M from a valid reviewer yet. Only full committers are accepted.
Even if an L-G-T-M may have been provided, it was from a non-committer,
_not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[Hannes Payer (out of office), 2015-08-27 13:23:27]

The CQ bit was unchecked by hpayer@chromium.org

[Hannes Payer (out of office), 2015-08-27 13:23:51]

lgtm

[Michael Starzinger, 2015-08-27 13:44:48]

The CQ bit was checked by mstarzinger@chromium.org

[commit-bot: I haz the power, 2015-08-27 13:44:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1305163007/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1305163007/20001

[commit-bot: I haz the power, 2015-08-27 13:57:44]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-08-27 13:58:00]

Patchset 2 (id:??) landed as
https://crrev.com/e276f5d89e2460dee1d5d925635622fbdb8580c2
Cr-Commit-Position: refs/heads/master@{#30412}