Remove unnecessary NoBarrier_load instructions in store buffer.

Remove unnecessary NoBarrier_load instructions in store buffer.

There are no stale store buffer pointers anymore. The sweeper thread can not be in conflict with store buffer processing.

BUG=

Committed: https://crrev.com/d49657edd70a6809c85ab5c60e55326e0317b01a
Cr-Commit-Position: refs/heads/master@{#27107}

[Hannes Payer (out of office), 2015-03-10 13:30:00]

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

[Jarin, 2015-03-10 13:32:25]

Almost lgtm.

https://codereview.chromium.org/993983002/diff/20001/src/heap/store-buffer.cc
File src/heap/store-buffer.cc (right):

https://codereview.chromium.org/993983002/diff/20001/src/heap/store-buffer.cc...
src/heap/store-buffer.cc:441: // which may be touched by the concurrent sweeper
thread.
Why did not you update this one?

[Hannes Payer (out of office), 2015-03-10 13:51:17]

https://codereview.chromium.org/993983002/diff/20001/src/heap/store-buffer.cc
File src/heap/store-buffer.cc (right):

https://codereview.chromium.org/993983002/diff/20001/src/heap/store-buffer.cc...
src/heap/store-buffer.cc:441: // which may be touched by the concurrent sweeper
thread.
On 2015/03/10 13:32:25, jarin wrote:
> Why did not you update this one?

Because the stale pointers may be accessed concurrently by the sweeper thread.
After executing this method we have valid pointers in the store buffer and don't
have to worry about the sweeper thread anymore.

[Hannes Payer (out of office), 2015-03-10 13:51:21]

The CQ bit was checked by hpayer@chromium.org

[commit-bot: I haz the power, 2015-03-10 13:51:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/993983002/20001

[commit-bot: I haz the power, 2015-03-10 14:19:18]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-03-10 14:19:33]

Patchset 2 (id:??) landed as
https://crrev.com/d49657edd70a6809c85ab5c60e55326e0317b01a
Cr-Commit-Position: refs/heads/master@{#27107}