Apply a patch to prevent an integer overflow in expat.

See https://www.mozilla.org/en-US/security/advisories/mfsa2015-54/ for Mozilla's advisory. Patch taken from https://hg.mozilla.org/releases/mozilla-esr31/rev/2f3e78643f5c

BUG=492052

Review URL: https://codereview.chromium.org/1151263010

Cr-Commit-Position: refs/heads/master@{#332964}
(cherry picked from commit 84ee0ec84f9de080e7d0e84dae6399d12c519d72)

Review URL: https://codereview.chromium.org/1224303003 .

Cr-Commit-Position: refs/branch-heads/2403@{#484}
Cr-Branched-From: f54b8097a9c45ed4ad308133d49f05325d6c5070-refs/heads/master@{#330231}
3 files changed