FFmpeg roll for M43.

Update FFmpegDemuxer::OnFindStreamInfoDone with the new
AVFormatContext layout.

BUG=465940

Review URL: https://codereview.chromium.org/1032543004

Cr-Commit-Position: refs/heads/master@{#322688}

DEPS

@@ -207,7 +207,7 @@ deps = {
    Var('chromium_git') + '/chromium/deps/libvpx.git' + '@' +  Var('libvpx_revision'),
 
   'src/third_party/ffmpeg':
-   Var('chromium_git') + '/chromium/third_party/ffmpeg.git' + '@' + 'b3dc5aa44575049edf6b24e34578487dfaade6a4',
+   Var('chromium_git') + '/chromium/third_party/ffmpeg.git' + '@' + 'f776b2743801160f7bf4377294b9a227f648fb21',
 
   'src/third_party/libjingle/source/talk':
     Var('chromium_git') + '/external/webrtc/trunk/talk.git' + '@' + '70cbec23cde10c3b81e591a58f153e83b1fcb74c',

media/ffmpeg/ffmpeg_common.h

@@ -32,6 +32,7 @@ extern "C" {
 MSVC_PUSH_DISABLE_WARNING(4244);
 #include <libavcodec/avcodec.h>
 #include <libavformat/avformat.h>
+#include <libavformat/internal.h>
 #include <libavformat/avio.h>
 #include <libavutil/avutil.h>
 #include <libavutil/imgutils.h>

media/filters/ffmpeg_demuxer.cc

@@ -838,10 +838,11 @@ void FFmpegDemuxer::OnFindStreamInfoDone(const PipelineStatusCB& status_cb,
   // If no estimate is found, the stream entry will be kInfiniteDuration().
   std::vector<base::TimeDelta> start_time_estimates(format_context->nb_streams,
                                                     kInfiniteDuration());
-  if (format_context->packet_buffer &&
+  const AVFormatInternal* internal = format_context->internal;
+  if (internal && internal->packet_buffer &&
       format_context->start_time != static_cast<int64>(AV_NOPTS_VALUE)) {
-    struct AVPacketList* packet_buffer = format_context->packet_buffer;
-    while (packet_buffer != format_context->packet_buffer_end) {
+    struct AVPacketList* packet_buffer = internal->packet_buffer;
+    while (packet_buffer != internal->packet_buffer_end) {
       DCHECK_LT(static_cast<size_t>(packet_buffer->pkt.stream_index),
                 start_time_estimates.size());
       const AVStream* stream =