Make AudioDebugFileWriter::AudioFileWriter use a SequencedTaskRunner

media/audio/audio_debug_file_writer.cc

Index: media/audio/audio_debug_file_writer.cc
diff --git a/media/audio/audio_debug_file_writer.cc b/media/audio/audio_debug_file_writer.cc
index ba181e9e4c24f3f98c27e20d3323e83884f139f2..583f9433b8198ce6da5e0ca646de771d23f879c0 100644
--- a/media/audio/audio_debug_file_writer.cc
+++ b/media/audio/audio_debug_file_writer.cc
@@ -12,6 +12,7 @@
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/sys_byteorder.h"
+#include "base/threading/thread_restrictions.h"
 #include "media/base/audio_bus.h"
 #include "media/base/audio_sample_types.h"
 
@@ -134,27 +135,22 @@ void WriteWavHeader(WavHeaderBuffer* buf,
 }  // namespace
 
 // Manages the debug recording file and writes to it. Can be created on any
-// thread. All the operations must be executed on |task_runner_|. Must be
-// destroyed on |task_runner_|.
+// thread. All the operations must be executed on a thread that has IO
+// permissions.
 class AudioDebugFileWriter::AudioFileWriter {
  public:
   static AudioFileWriterUniquePtr Create(
       const base::FilePath& file_name,
       const AudioParameters& params,
-      scoped_refptr<base::SingleThreadTaskRunner> task_runner);
+      scoped_refptr<base::SequencedTaskRunner> task_runner);
 
   ~AudioFileWriter();
 
   // Write data from |data| to file.
   void Write(const AudioBus* data);
 
-  scoped_refptr<base::SingleThreadTaskRunner> task_runner() {
-    return task_runner_;
-  }
-
  private:
-  AudioFileWriter(const AudioParameters& params,
-                  scoped_refptr<base::SingleThreadTaskRunner> task_runner);
+  AudioFileWriter(const AudioParameters& params);
 
   // Write wave header to file. Called on the |task_runner_| twice: on
   // construction
@@ -179,25 +175,26 @@ class AudioDebugFileWriter::AudioFileWriter {
   std::unique_ptr<int16_t[]> interleaved_data_;
   int interleaved_data_size_;
 
-  // The task runner this class operates on.
-  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  SEQUENCE_CHECKER(sequence_checker_);
 };
 
-AudioDebugFileWriter::OnThreadDeleter::OnThreadDeleter() {}
+AudioDebugFileWriter::OnSequenceDeleter::OnSequenceDeleter() {}
+
+AudioDebugFileWriter::OnSequenceDeleter::OnSequenceDeleter(
+    AudioDebugFileWriter::OnSequenceDeleter&& other) = default;
 
-AudioDebugFileWriter::OnThreadDeleter::OnThreadDeleter(
-    const OnThreadDeleter& other)
-    : task_runner_(other.task_runner_) {}
+AudioDebugFileWriter::OnSequenceDeleter&
+AudioDebugFileWriter::OnSequenceDeleter::operator=(
+    AudioDebugFileWriter::OnSequenceDeleter&&) = default;
 
-AudioDebugFileWriter::OnThreadDeleter::OnThreadDeleter(
-    scoped_refptr<base::SingleThreadTaskRunner> task_runner)
-    : task_runner_(task_runner) {}
+AudioDebugFileWriter::OnSequenceDeleter::OnSequenceDeleter(
+    scoped_refptr<base::SequencedTaskRunner> task_runner)
+    : task_runner_(std::move(task_runner)) {}
 
-AudioDebugFileWriter::OnThreadDeleter::~OnThreadDeleter() {}
+AudioDebugFileWriter::OnSequenceDeleter::~OnSequenceDeleter() {}
 
-// AudioFileWriter deleter. Inspired by
-// content::BrowserThread::DeleteOnFileThread.
-void AudioDebugFileWriter::OnThreadDeleter::operator()(
+// AudioFileWriter deleter.
+void AudioDebugFileWriter::OnSequenceDeleter::operator()(
     AudioDebugFileWriter::AudioFileWriter* ptr) const {
   if (!task_runner_->DeleteSoon(FROM_HERE, ptr)) {
 #if defined(UNIT_TEST)
@@ -213,9 +210,9 @@ AudioDebugFileWriter::AudioFileWriterUniquePtr
 AudioDebugFileWriter::AudioFileWriter::Create(
     const base::FilePath& file_name,
     const AudioParameters& params,
-    scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
-  AudioFileWriterUniquePtr file_writer(new AudioFileWriter(params, task_runner),
-                                       OnThreadDeleter(task_runner));
+    scoped_refptr<base::SequencedTaskRunner> task_runner) {
+  AudioFileWriterUniquePtr file_writer(new AudioFileWriter(params),
+                                       OnSequenceDeleter(task_runner));
 
   // base::Unretained is safe, because destructor is called on
   // |task_runner|.
@@ -227,21 +224,19 @@ AudioDebugFileWriter::AudioFileWriter::Create(
 }
 
 AudioDebugFileWriter::AudioFileWriter::AudioFileWriter(
-    const AudioParameters& params,
-    scoped_refptr<base::SingleThreadTaskRunner> task_runner)
-    : samples_(0),
-      params_(params),
-      interleaved_data_size_(0),
-      task_runner_(std::move(task_runner)) {}
+    const AudioParameters& params)
+    : samples_(0), params_(params), interleaved_data_size_(0) {
+  DETACH_FROM_SEQUENCE(sequence_checker_);
+}
 
 AudioDebugFileWriter::AudioFileWriter::~AudioFileWriter() {
-  DCHECK(task_runner_->BelongsToCurrentThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (file_.IsValid())
     WriteHeader();
 }
 
 void AudioDebugFileWriter::AudioFileWriter::Write(const AudioBus* data) {
-  DCHECK(task_runner_->BelongsToCurrentThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   DCHECK_EQ(params_.channels(), data->channels());
   if (!file_.IsValid())
     return;
@@ -268,7 +263,7 @@ void AudioDebugFileWriter::AudioFileWriter::Write(const AudioBus* data) {
 }
 
 void AudioDebugFileWriter::AudioFileWriter::WriteHeader() {
-  DCHECK(task_runner_->BelongsToCurrentThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!file_.IsValid())
     return;
   WavHeaderBuffer buf;
@@ -282,7 +277,8 @@ void AudioDebugFileWriter::AudioFileWriter::WriteHeader() {
 
 void AudioDebugFileWriter::AudioFileWriter::CreateRecordingFile(
     const base::FilePath& file_name) {
-  DCHECK(task_runner_->BelongsToCurrentThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+  base::ThreadRestrictions::AssertIOAllowed();
   DCHECK(!file_.IsValid());
 
   file_ = base::File(file_name,