Rejigger audio capture pipeline to work with separate main+worker threads (Mac).

media/audio/fake_audio_consumer.h

 // Copyright (c) 2013 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_FAKE_AUDIO_CONSUMER_H_
 #define MEDIA_AUDIO_FAKE_AUDIO_CONSUMER_H_
 
-#include "base/cancelable_callback.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/time.h"
-#include "media/audio/audio_parameters.h"
+#include "base/callback_forward.h"
+#include "base/memory/ref_counted.h"
+#include "media/base/media_export.h"
 
 namespace base {
 class MessageLoopProxy;
 }
 
 namespace media {
 class AudioBus;
+class AudioParameters;
 
 // A fake audio consumer.  Using a provided message loop, FakeAudioConsumer will
 // simulate a real time consumer of audio data.
 class MEDIA_EXPORT FakeAudioConsumer {
  public:
-  // |message_loop| is the loop on which the ReadCB provided to Start() will be
-  // executed on.  |params| is used to determine the frequency of callbacks.
-  FakeAudioConsumer(const scoped_refptr<base::MessageLoopProxy>& message_loop,
+  // |worker_loop| is the loop on which the ReadCB provided to Start() will be
+  // executed on.  This may or may not be the be for the same thread that
+  // invokes the Start/Stop methods.
+  // |params| is used to determine the frequency of callbacks.
+  FakeAudioConsumer(const scoped_refptr<base::MessageLoopProxy>& worker_loop,
                     const AudioParameters& params);
   ~FakeAudioConsumer();
 
-  // Start executing |read_cb| at a regular interval.  Must be called on the
-  // message loop provided during construction.  Stop() must be called before
-  // destroying FakeAudioConsumer.
+  // Start executing |read_cb| at a regular intervals.  Stop() must be called by
+  // the same thread before destroying FakeAudioConsumer.
   typedef base::Callback<void(AudioBus* audio_bus)> ReadCB;
   void Start(const ReadCB& read_cb);
 
-  // Stop executing the ReadCB provided to Start().  Cancels any outstanding
-  // callbacks.  Safe to call multiple times.  Must be called on the message
-  // loop provided during construction.
+  // Stop executing the ReadCB provided to Start().  Blocks until the worker
+  // loop is not inside a ReadCB invocation.  Safe to call multiple times.  Must
+  // be called on the same thread that called Start().
   void Stop();
 
  private:
-  // Task that regularly calls |read_cb_| according to the playback rate as
-  // determined by the audio parameters given during construction.  Runs on
-  // |message_loop_|.
-  void DoRead();
-
-  scoped_refptr<base::MessageLoopProxy> message_loop_;
-  ReadCB read_cb_;
-  scoped_ptr<AudioBus> audio_bus_;
-  base::TimeDelta buffer_duration_;
-  base::TimeTicks next_read_time_;
-
-  // Used to post delayed tasks to the AudioThread that we can cancel.
-  base::CancelableClosure read_task_cb_;
+  // All state and implementation is kept within this class because it must hang
+  // around until tasks posted on |worker_loop| have all run (or been canceled).
+  class Worker;
+  Worker* const worker_;
 
   DISALLOW_COPY_AND_ASSIGN(FakeAudioConsumer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_FAKE_AUDIO_CONSUMER_H_