Add acquire/release to global variable.

Add acquire/release to global variable.

In the case of subprocesses that create this after general
initialization, it's possible for the thread that is doing the
import is different than and created before the thread that
creates the GlobalHistogramAllocator.

Using release-store ensures that ctor initialization is complete
before the global pointer is written while acquire-load ensures
that all accesses to it come after the read of the global pointer.

BUG=689245
Review-Url: https://codereview.chromium.org/2684993008
Cr-Commit-Position: refs/heads/master@{#449407}
(cherry picked from commit 471e0a3d9789243b6db151544c8ca9da17b29f36)

Review-Url: https://codereview.chromium.org/2699953002 .
Cr-Commit-Position: refs/branch-heads/2987@{#554}
Cr-Branched-From: ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed: https://chromium.googlesource.com/chromium/src/+/3ce527bfb13aed34dacc1f2605222b2b01bd0347

[bcwhite, 2017-02-16 19:48:54]

Description was changed from

==========
Add acquire/release to global variable.

In the case of subprocesses that create this after general
initialization, it's possible for the thread that is doing the
import is different than and created before the thread that
creates the GlobalHistogramAllocator.

Using release-store ensures that ctor initialization is complete
before the global pointer is written while acquire-load ensures
that all accesses to it come after the read of the global pointer.

BUG=689245

Review-Url: https://codereview.chromium.org/2684993008
Cr-Commit-Position: refs/heads/master@{#449407}
(cherry picked from commit 471e0a3d9789243b6db151544c8ca9da17b29f36)
==========

to

==========
Add acquire/release to global variable.

In the case of subprocesses that create this after general
initialization, it's possible for the thread that is doing the
import is different than and created before the thread that
creates the GlobalHistogramAllocator.

Using release-store ensures that ctor initialization is complete
before the global pointer is written while acquire-load ensures
that all accesses to it come after the read of the global pointer.

BUG=689245

Review-Url: https://codereview.chromium.org/2684993008
Cr-Commit-Position: refs/heads/master@{#449407}
(cherry picked from commit 471e0a3d9789243b6db151544c8ca9da17b29f36)

Review-Url: https://codereview.chromium.org/2699953002 .
Cr-Commit-Position: refs/branch-heads/2987@{#554}
Cr-Branched-From:
ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed:
https://chromium.googlesource.com/chromium/src/+/3ce527bfb13aed34dacc1f260522...
==========

[bcwhite, 2017-02-16 19:48:55]

Committed patchset #1 (id:1) manually as
3ce527bfb13aed34dacc1f2605222b2b01bd0347.