Add a simple, safe gain PostProcessor.

chromecast/media/cma/backend/alsa/post_processing_pipeline_impl.h

 // Copyright 2017 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 CHROMECAST_MEDIA_CMA_BACKEND_ALSA_POST_PROCESSING_PIPELINE_IMPL_H_
 #define CHROMECAST_MEDIA_CMA_BACKEND_ALSA_POST_PROCESSING_PIPELINE_IMPL_H_
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "chromecast/media/cma/backend/alsa/post_processing_pipeline.h"
+#include "chromecast/media/cma/backend/alsa/post_processor_factory.h"
 
 namespace base {
 class ListValue;
-class ScopedNativeLibrary;
 }  // namespace base
 
 namespace chromecast {
 namespace media {
 
 class AudioPostProcessor;
 
 // Creates and contains multiple AudioPostProcessors, as specified in ctor.
 // Provides convenience methods to access and use the AudioPostProcessors.
 class PostProcessingPipelineImpl : public PostProcessingPipeline {
  public:
   PostProcessingPipelineImpl(const std::string& name,
                              const base::ListValue* filter_description_list,
                              int channels);
   ~PostProcessingPipelineImpl() override;
 
   int ProcessFrames(float* data,
                     int num_frames,
                     float current_volume,
                     bool is_silence) override;
 
   bool SetSampleRate(int sample_rate) override;
   bool IsRinging() override;
 
   // Send string |config| to post processor |name|.
   void SetPostProcessorConfig(const std::string& name,
                               const std::string& config) override;
 
  private:
+  // Note: typedef is used to silence chromium-style mandatory constructor in
+  // structs.
+  typedef struct {
+    std::unique_ptr<AudioPostProcessor> ptr;
+    std::string name;
+  } PostProcessorInfo;
+
   int GetRingingTimeInFrames();
   void UpdateCastVolume(float multiplier);
 
   std::string name_;
   int sample_rate_;
   int ringing_time_in_frames_ = 0;
   int silence_frames_processed_ = 0;
   int total_delay_frames_ = 0;
   float current_multiplier_;
   float cast_volume_;
 
-  // Contains all libraries in use;
-  // Functions in shared objects cannot be used once library is closed.
-  std::vector<std::unique_ptr<base::ScopedNativeLibrary>> libraries_;
-
-  // Must be after libraries_
-  // Note: typedef is used to silence chromium-style mandatory constructor in
-  // structs.
-  typedef struct {
-    std::unique_ptr<AudioPostProcessor> ptr;
-    std::string name;
-  } PostProcessorInfo;
+  // factory_ keeps shared libraries open, so it must outlive processors_.
+  PostProcessorFactory factory_;
 
   std::vector<PostProcessorInfo> processors_;
 
   DISALLOW_COPY_AND_ASSIGN(PostProcessingPipelineImpl);
 };
 
 }  // namespace media
 }  // namespace chromecast
 
 #endif  // CHROMECAST_MEDIA_CMA_BACKEND_ALSA_POST_PROCESSING_PIPELINE_IMPL_H_