Update expat to 2.2.0 to fix CVE vulnerability.

Update expat to 2.2.0 to fix CVE vulnerability.

Security fixes:
    CVE-2016-0718 -- Fix crash on malformed input
    CVE-2016-4472 -- Improve insufficient fix to CVE-2015-1283 /
    CVE-2015-2716 introduced with Expat 2.1.1
    CVE-2016-5300 -- Use more entropy for hash initialization
        than the original fix to CVE-2012-0876
    CVE-2012-6702 -- Resolve troublesome internal call to srand
            that was introduced with Expat 2.1.0
            when addressing CVE-2012-0876 (issue #496)

BUG=703537
Review-Url: https://codereview.chromium.org/2761253002
Cr-Commit-Position: refs/heads/master@{#459025}
(cherry picked from commit 33a5703a620ec246ee08214e6c880068b6e9d687)

Review-Url: https://codereview.chromium.org/2781503002 .
Cr-Commit-Position: refs/branch-heads/3029@{#425}
Cr-Branched-From: 939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}
Committed: https://chromium.googlesource.com/chromium/src/+/55a2d106eda76d4248ba3415d4718afd7538f425

[dominicc (has gone to gerrit), 2017-03-27 13:34:13]

Description was changed from

==========
Update expat to 2.2.0 to fix CVE vulnerability.

Security fixes:
    CVE-2016-0718 -- Fix crash on malformed input
    CVE-2016-4472 -- Improve insufficient fix to CVE-2015-1283 /
    CVE-2015-2716 introduced with Expat 2.1.1
    CVE-2016-5300 -- Use more entropy for hash initialization
        than the original fix to CVE-2012-0876
    CVE-2012-6702 -- Resolve troublesome internal call to srand
            that was introduced with Expat 2.1.0
            when addressing CVE-2012-0876 (issue #496)

BUG=703537

Review-Url: https://codereview.chromium.org/2761253002
Cr-Commit-Position: refs/heads/master@{#459025}
(cherry picked from commit 33a5703a620ec246ee08214e6c880068b6e9d687)
==========

to

==========
Update expat to 2.2.0 to fix CVE vulnerability.

Security fixes:
    CVE-2016-0718 -- Fix crash on malformed input
    CVE-2016-4472 -- Improve insufficient fix to CVE-2015-1283 /
    CVE-2015-2716 introduced with Expat 2.1.1
    CVE-2016-5300 -- Use more entropy for hash initialization
        than the original fix to CVE-2012-0876
    CVE-2012-6702 -- Resolve troublesome internal call to srand
            that was introduced with Expat 2.1.0
            when addressing CVE-2012-0876 (issue #496)

BUG=703537

Review-Url: https://codereview.chromium.org/2761253002
Cr-Commit-Position: refs/heads/master@{#459025}
(cherry picked from commit 33a5703a620ec246ee08214e6c880068b6e9d687)

Review-Url: https://codereview.chromium.org/2781503002 .
Cr-Commit-Position: refs/branch-heads/3029@{#425}
Cr-Branched-From:
939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}
Committed:
https://chromium.googlesource.com/chromium/src/+/55a2d106eda76d4248ba3415d471...
==========

[dominicc (has gone to gerrit), 2017-03-27 13:34:16]

Committed patchset #1 (id:1) manually as
55a2d106eda76d4248ba3415d4718afd7538f425.