Audio input debug recording refactoring to reduce thread hops and simplify object ownership

media/audio/audio_input_writer.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_AUDIO_AUDIO_INPUT_WRITER_H_
 #define MEDIA_AUDIO_AUDIO_INPUT_WRITER_H_
 
 #include <memory>
 
 namespace media {
 
 class AudioBus;
 
 // A writer interface used by AudioInputController for writing audio data to
 // file for debugging purposes.
 class AudioInputWriter {
  public:
   virtual ~AudioInputWriter() {}
 
+  // Must be called before calling Write() for the first time after creation or
+  // Stop() call. Can be called on any sequence; Write() and Stop() must be
+  // called on the same sequence as Start().
+  virtual void Start(const base::FilePath& file) = 0;
+
+  // Must be called to finish recording. Each call to Start() requires a call to
+  // Stop(). Will be automatically called on destruction.
+  virtual void Stop() = 0;
+
   // Write |data| to file.
   virtual void Write(std::unique_ptr<AudioBus> data) = 0;
+
+  // Returns true if Write() call scheduled at this point will most likely write
+  // data to the file, and false if it most likely will be a no-op. The result
+  // may be ambigulous if Start() or Stop() is executed at the moment. Can be
+  // called from any sequence.
+  virtual bool WillWrite() = 0;
 };
 
 }  // namspace media
 
 #endif  // MEDIA_AUDIO_AUDIO_INPUT_WRITER_H_