Roll src/third_party/ffmpeg/ bfe62e18d..bbe6b81a6 (4 commits)

https://chromium.googlesource.com/chromium/third_party/ffmpeg.git/+log/bfe62e18d24f..bbe6b81a6c31

$ git log bfe62e18d..bbe6b81a6 --date=short --no-merges --format='%ad %ae %s'
2018-09-10 dalecurtis Update patches file for new ffmpeg fixes.
2018-09-07 dalecurtis avformat/utils: Don't calculate duration using AV_NOPTS_VALUE for start_time.
2018-08-30 dalecurtis avformat/mov: Error on too large stsd entry counts.
2018-08-22 liberato Fetch upstream and check for upstream commit.

Created with:
  roll-dep src/third_party/ffmpeg

BUG=879852, 826648
TBR=tguilbert

Change-Id: Ibdec4e7e2ffd3d7d61bdefa71f09814d699bba5b
Reviewed-on: https://chromium-review.googlesource.com/1217040Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Thomas Guilbert <tguilbert@chromium.org>
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590062}

DEPS

@@ -644,7 +644,7 @@ deps = {
   },
 
   'src/third_party/ffmpeg':
-    Var('chromium_git') + '/chromium/third_party/ffmpeg.git' + '@' + 'bfe62e18d24fc49234c29941e7dd9152f099e99b',
+    Var('chromium_git') + '/chromium/third_party/ffmpeg.git' + '@' + 'bbe6b81a6c310d4931cc8a5164d1a374652e054a',
 
   'src/third_party/flac':
     Var('chromium_git') + '/chromium/deps/flac.git' + '@' + 'af862024c8c8fa0ae07ced05e89013d881b00596',