Replace FFmpegDemuxer thread per element with base::TaskScheduler.

media/test/run_all_unittests.cc

Index: media/test/run_all_unittests.cc
diff --git a/media/test/run_all_unittests.cc b/media/test/run_all_unittests.cc
index 57d384c676a1aa18fe73c0ff416b735c2521fe00..681cc7d9bba9e36f1b267bf66f582b96b119828a 100644
--- a/media/test/run_all_unittests.cc
+++ b/media/test/run_all_unittests.cc
@@ -4,6 +4,7 @@
 
 #include "base/bind.h"
 #include "base/command_line.h"
+#include "base/task_scheduler/task_scheduler.h"
 #include "base/test/launcher/unit_test_launcher.h"
 #include "base/test/test_discardable_memory_allocator.h"
 #include "base/test/test_suite.h"
@@ -56,6 +57,7 @@ void TestSuiteNoAtExit::Initialize() {
   media::InitializeMediaLibrary();
   media::SetUpFakeLocalizedStrings();
 
+  base::TaskScheduler::CreateAndSetSimpleTaskScheduler(1);

[gab, 2017/02/23 21:37:10]

base::test::ScopedTaskScheduler (we typically prefer to only put it in fixtures
that need it but if all your tests need it it's your call if you want it here)

   base::DiscardableMemoryAllocator::SetInstance(&discardable_memory_allocator_);
 }