Introduced the new parameter setting scheme for activating the high-pass filter in APM

webrtc/modules/audio_processing/audio_processing_impl.h

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 106 matching lines @@
       EXCLUSIVE_LOCKS_REQUIRED(crit_capture_);
 
   // Methods returning pointers to APM submodules.
   // No locks are aquired in those, as those locks
   // would offer no protection (the submodules are
   // created only once in a single-treaded manner
   // during APM creation).
   EchoCancellation* echo_cancellation() const override;
   EchoControlMobile* echo_control_mobile() const override;
   GainControl* gain_control() const override;
+  // TODO(peah): Deprecate this API call.
   HighPassFilter* high_pass_filter() const override;
   LevelEstimator* level_estimator() const override;
   NoiseSuppression* noise_suppression() const override;
   VoiceDetection* voice_detection() const override;
 
+  // TODO(peah): Remove when the HighPassFilter interface has been removed.
+  void EnableHighPassFilter(bool enable);

[the sun, 2016/10/26 09:06:43]

How about you simply expose a "const AudioProcessing::Config& config() const;"
method and use that +ApplyConfig() in you HPFImpl? I think it will scale better
when you update the other submodule APIs.

[peah-webrtc, 2016/10/28 05:50:28]

Great suggestion! 
Done.

+  bool IsHighPassFilterEnabled();
+
  protected:
   // Overridden in a mock.
   virtual int InitializeLocked()
       EXCLUSIVE_LOCKS_REQUIRED(crit_render_, crit_capture_);
 
  private:
   // TODO(peah): These friend classes should be removed as soon as the new
   // parameter setting scheme allows.
   FRIEND_TEST_ALL_PREFIXES(ApmConfiguration, DefaultBehavior);
   FRIEND_TEST_ALL_PREFIXES(ApmConfiguration, ValidConfigBehavior);
@@ skipping 85 matching lines @@
   // acquired.
   void InitializeTransient()
       EXCLUSIVE_LOCKS_REQUIRED(crit_render_, crit_capture_);
   void InitializeBeamformer()
       EXCLUSIVE_LOCKS_REQUIRED(crit_render_, crit_capture_);
   void InitializeIntelligibility()
       EXCLUSIVE_LOCKS_REQUIRED(crit_render_, crit_capture_);
   int InitializeLocked(const ProcessingConfig& config)
       EXCLUSIVE_LOCKS_REQUIRED(crit_render_, crit_capture_);
   void InitializeLevelController() EXCLUSIVE_LOCKS_REQUIRED(crit_capture_);
+  void InitializeHighPassFilter() EXCLUSIVE_LOCKS_REQUIRED(crit_capture_);
 
   void EmptyQueuedRenderAudio();
   void AllocateRenderQueue()
       EXCLUSIVE_LOCKS_REQUIRED(crit_render_, crit_capture_);
   void QueueRenderAudio(const AudioBuffer* audio)
       EXCLUSIVE_LOCKS_REQUIRED(crit_render_);
 
   // Capture-side exclusive methods possibly running APM in a multi-threaded
   // manner that are called with the render lock already acquired.
   int ProcessCaptureStreamLocked() EXCLUSIVE_LOCKS_REQUIRED(crit_capture_);
@@ skipping 130 matching lines @@
   std::vector<float> capture_queue_buffer_ GUARDED_BY(crit_capture_);
 
   // Lock protection not needed.
   std::unique_ptr<SwapQueue<std::vector<float>, RenderQueueItemVerifier<float>>>
       render_signal_queue_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_AUDIO_PROCESSING_IMPL_H_