Roll src/third_party/ffmpeg 4b95e27:1de28af

Roll src/third_party/ffmpeg 4b95e27:1de28af

Fixes null ref crash in matroska_read_seek.

Summary of changes available at:
https://chromium.googlesource.com/chromium/third_party/ffmpeg/+log/4b95e27..1de28af

BUG=484423
TEST=Manual verification of clusterfuzz test case.

Committed: https://crrev.com/ba6f68ca9e93654011350088c8a986dd3d0938ac
Cr-Commit-Position: refs/heads/master@{#360508}

[chcunningham, 2015-11-19 00:32:04]

chcunningham@chromium.org changed reviewers:
+ ddorwin@chromium.org

[ddorwin, 2015-11-19 00:40:54]

lgtm

[chcunningham, 2015-11-19 00:42:36]

The CQ bit was checked by chcunningham@chromium.org

[commit-bot: I haz the power, 2015-11-19 00:46:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1454283002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1454283002/1

[chcunningham, 2015-11-19 01:38:59]

The CQ bit was unchecked by chcunningham@chromium.org

[chcunningham, 2015-11-19 01:40:07]

The CQ bit was checked by chcunningham@chromium.org

[commit-bot: I haz the power, 2015-11-19 01:40:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1454283002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1454283002/1

[commit-bot: I haz the power, 2015-11-19 03:09:49]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-19 03:10:56]

Patchset 1 (id:??) landed as
https://crrev.com/ba6f68ca9e93654011350088c8a986dd3d0938ac
Cr-Commit-Position: refs/heads/master@{#360508}