Replace FFmpegDemuxer thread per element with base::TaskScheduler.

chromecast/media/cma/test/frame_segmenter_for_test.cc

Index: chromecast/media/cma/test/frame_segmenter_for_test.cc
diff --git a/chromecast/media/cma/test/frame_segmenter_for_test.cc b/chromecast/media/cma/test/frame_segmenter_for_test.cc
index 25b4b8d30812c56bfd576d0a44a194ccf1604000..75a0292ea3a1c07346e1d34b97593218bc35bb8a 100644
--- a/chromecast/media/cma/test/frame_segmenter_for_test.cc
+++ b/chromecast/media/cma/test/frame_segmenter_for_test.cc
@@ -9,7 +9,9 @@
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/logging.h"
+#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_task_scheduler.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "chromecast/media/cma/base/decoder_buffer_adapter.h"
 #include "media/base/decoder_buffer.h"
@@ -313,6 +315,7 @@ DemuxResult FFmpegDemuxForTest(const base::FilePath& filepath,
   ::media::FileDataSource data_source;
   CHECK(data_source.Initialize(filepath));
 
+  base::test::ScopedTaskScheduler task_scheduler(base::MessageLoop::current());

[gab, 2017/02/26 18:01:35]

There should really just be one ScopedTaskScheduler in the whole scope of a
test, bringing it in&out in a helper method is unexpected.

Can we put one in the fixture of audio_video_pipeline_device_unittest.cc where
this seems to be used instead?

[DaleCurtis, 2017/02/27 21:26:30]

Done, but took a few more changes.

   ::media::FFmpegDemuxer demuxer(
       base::ThreadTaskRunnerHandle::Get(), &data_source,
       base::Bind(&OnEncryptedMediaInitData), base::Bind(&OnMediaTracksUpdated),