Replace FFmpegDemuxer thread per element with base::TaskScheduler.

media/base/demuxer_perftest.cc

Index: media/base/demuxer_perftest.cc
diff --git a/media/base/demuxer_perftest.cc b/media/base/demuxer_perftest.cc
index adfde41002e92b4e49a849cf8b7197f41fa76f32..3485e97589198a2f5821fea77e1508bd0121f0ba 100644
--- a/media/base/demuxer_perftest.cc
+++ b/media/base/demuxer_perftest.cc
@@ -12,6 +12,7 @@
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/test/scoped_task_scheduler.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
@@ -48,20 +49,19 @@ class DemuxerHostImpl : public media::DemuxerHost {
   DISALLOW_COPY_AND_ASSIGN(DemuxerHostImpl);
 };
 
-static void QuitLoopWithStatus(base::MessageLoop* message_loop,
+static void QuitLoopWithStatus(base::Closure quit_cb,
                                media::PipelineStatus status) {
   CHECK_EQ(status, media::PIPELINE_OK);
-  message_loop->task_runner()->PostTask(
-      FROM_HERE, base::MessageLoop::QuitWhenIdleClosure());
+  quit_cb.Run();
 }
 
 static void OnEncryptedMediaInitData(EmeInitDataType init_data_type,
                                      const std::vector<uint8_t>& init_data) {
-  VLOG(0) << "File is encrypted.";
+  DVLOG(1) << "File is encrypted.";
 }
 
 static void OnMediaTracksUpdated(std::unique_ptr<MediaTracks> tracks) {
-  VLOG(0) << "Got media tracks info, tracks = " << tracks->tracks().size();
+  DVLOG(1) << "Got media tracks info, tracks = " << tracks->tracks().size();
 }
 
 typedef std::vector<media::DemuxerStream* > Streams;
@@ -177,10 +177,10 @@ int StreamReader::GetNextStreamIndexToRead() {
 
 static void RunDemuxerBenchmark(const std::string& filename) {
   base::FilePath file_path(GetTestDataFilePath(filename));
-  double total_time = 0.0;
+  base::TimeDelta total_time;
   for (int i = 0; i < kBenchmarkIterations; ++i) {
     // Setup.
-    base::MessageLoop message_loop;
+    base::test::ScopedTaskScheduler scoped_task_scheduler;
     DemuxerHostImpl demuxer_host;
     FileDataSource data_source;
     ASSERT_TRUE(data_source.Initialize(file_path));
@@ -189,34 +189,38 @@ static void RunDemuxerBenchmark(const std::string& filename) {
         base::Bind(&OnEncryptedMediaInitData);
     Demuxer::MediaTracksUpdatedCB tracks_updated_cb =
         base::Bind(&OnMediaTracksUpdated);
-    FFmpegDemuxer demuxer(message_loop.task_runner(), &data_source,
+    FFmpegDemuxer demuxer(base::ThreadTaskRunnerHandle::Get(), &data_source,
                           encrypted_media_init_data_cb, tracks_updated_cb,
                           new MediaLog());
 
-    demuxer.Initialize(&demuxer_host,
-                       base::Bind(&QuitLoopWithStatus, &message_loop),
-                       false);
-    base::RunLoop().Run();
+    {
+      base::RunLoop run_loop;
+      demuxer.Initialize(
+          &demuxer_host,
+          base::Bind(&QuitLoopWithStatus, run_loop.QuitClosure()), false);
+      run_loop.Run();
+    }
+
     StreamReader stream_reader(&demuxer, false);
 
     // Benchmark.
     base::TimeTicks start = base::TimeTicks::Now();
-    while (!stream_reader.IsDone()) {
+    while (!stream_reader.IsDone())
       stream_reader.Read();
-    }
-    base::TimeTicks end = base::TimeTicks::Now();
-    total_time += (end - start).InSecondsF();
+    total_time += base::TimeTicks::Now() - start;
     demuxer.Stop();
-    QuitLoopWithStatus(&message_loop, PIPELINE_OK);
-    base::RunLoop().Run();
+
+    {
+      base::RunLoop run_loop;
+      base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
+                                                    run_loop.QuitClosure());
+      run_loop.Run();

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

This whole block can be replaced by base::RunLoop().RunUntilIdle(); I think
(unless you really care to strictly only run tasks already posted but not tasks
posted from those, if any?)

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

Done.

+    }
   }
 
-  perf_test::PrintResult("demuxer_bench",
-                         "",
-                         filename,
-                         kBenchmarkIterations / total_time,
-                         "runs/s",
-                         true);
+  perf_test::PrintResult("demuxer_bench", "", filename,
+                         kBenchmarkIterations / total_time.InSecondsF(),
+                         "runs/s", true);
 }
 
 #if defined(OS_WIN)