[Cast] Track audio queued in encoder; account for it in ShouldDropNextFrame().

media/cast/sender/audio_encoder.h

 // Copyright 2014 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_CAST_SENDER_AUDIO_ENCODER_H_
 #define MEDIA_CAST_SENDER_AUDIO_ENCODER_H_
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/threading/thread_checker.h"
 #include "media/base/audio_bus.h"
 #include "media/cast/cast_environment.h"
 
 namespace base {
 class TimeTicks;
 }
 
 namespace media {
 namespace cast {
 
 class AudioEncoder {
  public:
-  typedef base::Callback<void(scoped_ptr<EncodedFrame>)>
+  // Callback to deliver each EncodedFrame, plus the number of audio samples
+  // skipped since the last frame.
+  typedef base::Callback<void(scoped_ptr<EncodedFrame>, int)>
       FrameEncodedCallback;
 
   AudioEncoder(const scoped_refptr<CastEnvironment>& cast_environment,
                int num_channels,
                int sampling_rate,
                int bitrate,
                Codec codec,
                const FrameEncodedCallback& frame_encoded_callback);
   virtual ~AudioEncoder();
 
   CastInitializationStatus InitializationResult() const;
 
+  int GetSamplesPerFrame() const;
+
   void InsertAudio(scoped_ptr<AudioBus> audio_bus,
                    const base::TimeTicks& recorded_time);
 
  private:
   class ImplBase;
   class OpusImpl;
   class Pcm16Impl;
 
   const scoped_refptr<CastEnvironment> cast_environment_;
   scoped_refptr<ImplBase> impl_;
 
   // Used to ensure only one thread invokes InsertAudio().
   base::ThreadChecker insert_thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioEncoder);
 };
 
 }  // namespace cast
 }  // namespace media
 
 #endif  // MEDIA_CAST_SENDER_AUDIO_ENCODER_H_