zlib: Remove Windows XP workaround for CPU feature detection

zlib: Remove Windows XP workaround for CPU feature detection

XP didn't have InitOnceExecuteOnce() so it was necessary to implement an
equivalent using atomic compare-and-swap. With XP support no longer necessary
the CPU feature detection code can now use InitOnceExecuteOnce() directly.

TEST=net_unittests(GZipUnitTest)
BUG=587964
Committed: https://crrev.com/18ad5f3a40ceab583961ca5dc064e01900514c57
Cr-Commit-Position: refs/heads/master@{#377928}

[robert.bradford, 2016-02-18 18:30:55]

The CQ bit was checked by robert.bradford@intel.com to run a CQ dry run

[commit-bot: I haz the power, 2016-02-18 18:35:08]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1711683003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1711683003/1

[commit-bot: I haz the power, 2016-02-18 19:39:49]

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

[commit-bot: I haz the power, 2016-02-18 19:39:50]

Dry run: This issue passed the CQ dry run.

[robert.bradford, 2016-02-18 20:48:39]

Description was changed from

==========
zlib: Remove Windows XP workaround for CPU feature detection

XP didn't have InitOnceExecuteOnce() so it was necessary to implement
the equivalent. With XP support no longer necessary this technical debt
can be repaid.

TEST=net_unittests(GZipUnitTest)
BUG=<TO BE FILED>
==========

to

==========
zlib: Remove Windows XP workaround for CPU feature detection

XP didn't have InitOnceExecuteOnce() so it was necessary to implement an
equivalent using atomic compare-and-swap. With XP support no longer necessary
the CPU feature detection code can now use InitOnceExecuteOnce() directly.

TEST=net_unittests(GZipUnitTest)
BUG=587964
==========

[robert.bradford, 2016-02-18 20:53:49]

robert.bradford@intel.com changed reviewers:
+ agl@chromium.org

[robert.bradford, 2016-02-18 20:53:49]

robert.bradford@intel.com changed required reviewers:
+ agl@chromium.org

[robert.bradford, 2016-02-18 20:53:50]

Hi agl@ please could you take a look? If it's fine please CQ.

[robert.bradford, 2016-02-26 16:56:49]

agl@ ping?

[robert.bradford, 2016-02-26 16:57:01]

agl@ ping?

[agl, 2016-02-26 17:00:02]

please wrap lines at 80 chars. Otherwise LGTM.

[robert.bradford, 2016-02-26 17:18:34]

The CQ bit was checked by robert.bradford@intel.com

[robert.bradford, 2016-02-26 17:18:34]

The patchset sent to the CQ was uploaded after l-g-t-m from agl@chromium.org
Link to the patchset: https://codereview.chromium.org/1711683003/#ps20001
(title: "80 char tidy up")

[commit-bot: I haz the power, 2016-02-26 17:20:22]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1711683003/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1711683003/20001

[commit-bot: I haz the power, 2016-02-26 18:30:37]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-02-26 18:31:52]

Description was changed from

==========
zlib: Remove Windows XP workaround for CPU feature detection

XP didn't have InitOnceExecuteOnce() so it was necessary to implement an
equivalent using atomic compare-and-swap. With XP support no longer necessary
the CPU feature detection code can now use InitOnceExecuteOnce() directly.

TEST=net_unittests(GZipUnitTest)
BUG=587964
==========

to

==========
zlib: Remove Windows XP workaround for CPU feature detection

XP didn't have InitOnceExecuteOnce() so it was necessary to implement an
equivalent using atomic compare-and-swap. With XP support no longer necessary
the CPU feature detection code can now use InitOnceExecuteOnce() directly.

TEST=net_unittests(GZipUnitTest)
BUG=587964

Committed: https://crrev.com/18ad5f3a40ceab583961ca5dc064e01900514c57
Cr-Commit-Position: refs/heads/master@{#377928}
==========

[commit-bot: I haz the power, 2016-02-26 18:31:53]

Patchset 2 (id:??) landed as
https://crrev.com/18ad5f3a40ceab583961ca5dc064e01900514c57
Cr-Commit-Position: refs/heads/master@{#377928}