Fix missing seek information when video has no start time.

media/filters/ffmpeg_demuxer_unittest.cc

Index: media/filters/ffmpeg_demuxer_unittest.cc
diff --git a/media/filters/ffmpeg_demuxer_unittest.cc b/media/filters/ffmpeg_demuxer_unittest.cc
index 636b75735469e55e16ce6b63f88be85273c23cc1..2cfcee225359eae6a9379da797f9de0d3c895e4c 100644
--- a/media/filters/ffmpeg_demuxer_unittest.cc
+++ b/media/filters/ffmpeg_demuxer_unittest.cc
@@ -193,6 +193,10 @@ class FFmpegDemuxerTest : public testing::Test {
     return demuxer_->glue_->format_context();
   }
 
+  int preferred_seeking_stream_index() const {
+    return demuxer_->preferred_stream_for_seeking_.first;
+  }
+
   void ReadUntilEndOfStream(DemuxerStream* stream) {
     bool got_eos_buffer = false;
     const int kMaxBuffers = 170;
@@ -412,6 +416,12 @@ TEST_F(FFmpegDemuxerTest, Read_Text) {
   message_loop_.Run();
 }
 
+TEST_F(FFmpegDemuxerTest, SeekInitialized_NoVideoStartTime) {
+  CreateDemuxer("audio-start-time-only.webm");
+  InitializeDemuxer();
+  EXPECT_EQ(0, preferred_seeking_stream_index());
+}
+
 TEST_F(FFmpegDemuxerTest, Read_VideoPositiveStartTime) {
   const int64 kTimelineOffsetMs = 1352550896000LL;