[unpacker] Add a disable flag for the new zip unpacker.

[unpacker] Add a disable flag for the new zip unpacker.

This patch adds a flag to disable the new zip unpacker. Note, that this flag
is not used yet.

TEST=unit_tests: *AboutFlagsHistogramTest*
BUG=427775
Committed: https://crrev.com/644ca400689094e521619420d84288cd3c554e43
Cr-Commit-Position: refs/heads/master@{#301998}

[mtomasz, 2014-10-29 03:50:30]

mtomasz@chromium.org changed reviewers:
+ fukino@chromium.org

[mtomasz, 2014-10-29 03:50:38]

@fukino: PTAL. Thanks!

[fukino, 2014-10-29 03:55:34]

On 2014/10/29 03:50:38, mtomasz wrote:
> @fukino: PTAL. Thanks!

lgtm.

[mtomasz, 2014-10-29 03:59:54]

The CQ bit was checked by mtomasz@chromium.org

[commit-bot: I haz the power, 2014-10-29 04:00:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/683413002/1

[commit-bot: I haz the power, 2014-10-29 04:06:23]

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

[commit-bot: I haz the power, 2014-10-29 04:06:24]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[mtomasz, 2014-10-29 04:09:03]

mtomasz@chromium.org changed reviewers:
+ isherman@chromium.org

[mtomasz, 2014-10-29 04:09:12]

@isherman: PTAL at IDL.

[mtomasz, 2014-10-30 00:26:23]

On 2014/10/29 04:09:12, mtomasz wrote:
> @isherman: PTAL at IDL.

@isherman: Friendly ping.

[Ilya Sherman, 2014-10-30 00:45:41]

histograms lgtm

[mtomasz, 2014-10-30 00:46:44]

The CQ bit was checked by mtomasz@chromium.org

[commit-bot: I haz the power, 2014-10-30 00:48:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/683413002/1

[commit-bot: I haz the power, 2014-10-30 00:51:51]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-30 00:52:33]

Patchset 1 (id:??) landed as
https://crrev.com/644ca400689094e521619420d84288cd3c554e43
Cr-Commit-Position: refs/heads/master@{#301998}