M54: Roll FFmpeg 75976ae..cf2d534b

https://chromium.googlesource.com/chromium/third_party/ffmpeg/+log/75976ae..cf2d534b

cf2d534 avformat/mov: Fix potential integer overflow in mov_read_keys

BUG=643948
TBR=xhwang@chromium.org

Review URL: https://codereview.chromium.org/2453323005 .

Cr-Commit-Position: refs/branch-heads/2840@{#791}
Cr-Branched-From: 1ae106dbab4bddd85132d5b75c670794311f4c57-refs/heads/master@{#414607}
1 file changed