Roll src/third_party/ffmpeg/ fa04e15e1..68b4dfdbd (429 commits)

https://chromium.googlesource.com/chromium/third_party/ffmpeg.git/+log/fa04e15e1ad6..68b4dfdbd607

$ git log fa04e15e1..68b4dfdbd --date=short --no-merges --format='%ad %ae %s'
2019-12-04 tguilbert README.chromium file
2019-12-04 tguilbert GN Configuration
2019-12-03 hwrenx lavc/libxavs2.c: optimize error descriptions
2019-12-03 hwrenx lavc/libxavs2.c: fix code style - spaces
2019-12-03 hwrenx lavc/libxavs2.c: avoid recomputations of pointers in xavs2_copy_frame* functions
(...)
2019-10-22 andreas.rheinhardt avformat/mpeg: Don't free unintialized pointer
2019-10-23 ramiro.polla mpegvideo_enc: add intra_penalty option for p frames
2019-10-23 andreas.rheinhardt avformat/icoenc: Add deinit function
2019-10-23 andreas.rheinhardt avformat/aiffenc: Use better error codes
2019-10-22 andreas.rheinhardt avformat/mpeg: Add padding to extradata

Created with:
  roll-dep src/third_party/ffmpeg

Bug: 1031252
Change-Id: Ie4dce5c2112c018b9353b7244391e1682ed37134
TBR: tmathmeyer
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1956258Reviewed-by: Thomas Guilbert <tguilbert@chromium.org>
Reviewed-by: Ted Meyer <tmathmeyer@chromium.org>
Commit-Queue: Thomas Guilbert <tguilbert@chromium.org>
Auto-Submit: Thomas Guilbert <tguilbert@chromium.org>
Cr-Commit-Position: refs/heads/master@{#723480}

DEPS

@@ -911,7 +911,7 @@ deps = {
   },
 
   'src/third_party/ffmpeg':
-    Var('chromium_git') + '/chromium/third_party/ffmpeg.git' + '@' + 'fa04e15e1ad61052e85f42413d4b841d2a496ec0',
+    Var('chromium_git') + '/chromium/third_party/ffmpeg.git' + '@' + '68b4dfdbd607fdd33b9b8e3515f039d97677dd1c',
 
   'src/third_party/flac':
     Var('chromium_git') + '/chromium/deps/flac.git' + '@' + 'af862024c8c8fa0ae07ced05e89013d881b00596',