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

webrtc/modules/audio_processing/audio_processing_impl.h

Index: webrtc/modules/audio_processing/audio_processing_impl.h
diff --git a/webrtc/modules/audio_processing/audio_processing_impl.h b/webrtc/modules/audio_processing/audio_processing_impl.h
index aec4ed7086d992b3bcb01d154a5d49f1dc392406..eb88484d7e485cefefa605c3b7de0c2b19f53f95 100644
--- a/webrtc/modules/audio_processing/audio_processing_impl.h
+++ b/webrtc/modules/audio_processing/audio_processing_impl.h
@@ -22,6 +22,7 @@
 #include "webrtc/base/swap_queue.h"
 #include "webrtc/base/thread_annotations.h"
 #include "webrtc/modules/audio_processing/audio_buffer.h"
+#include "webrtc/modules/audio_processing/high_pass_filter_impl.h"
 #include "webrtc/modules/audio_processing/include/audio_processing.h"
 #include "webrtc/modules/audio_processing/render_queue_item_verifier.h"
 #include "webrtc/system_wrappers/include/file_wrapper.h"
@@ -124,11 +125,27 @@ class AudioProcessingImpl : public AudioProcessing {
   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 these two methods once the new API allows that.
+  template <typename MutatorFunction>
+  void MutateConfig(MutatorFunction mutator) {

[the sun, 2016/10/28 10:52:53]

Nice! Can we do without it being a template though? The function prototype
should be the same in all cases. You should probably use rtc::FunctionView<>, or
possibly std::function - check with Karl what is the preferred way.

(See
https://chromium.googlesource.com/external/webrtc/+/master/webrtc/modules/aud...
for an example use of rtc::FunctionView<>)

[kwiberg-webrtc, 2016/10/28 11:07:00]

rtc::FunctionView is the right thing to use in a case like this, when the callee
isn't allowed to save the function. However, since this method is simple and not
virtual, I think using a template is fine too (but consider using const& or &&
so that you pass the mutator by reference instead of by value).

[peah-webrtc, 2016/10/28 12:19:52]

Great suggestion!
Done.

[peah-webrtc, 2016/10/28 12:19:52]

Thanks! I think the FunctionView became really nice in this case so I used that.

Done.

[kwiberg-webrtc, 2016/10/28 12:28:56]

No, you used std::function instead (which will also work, although it's a bit
more expensive since it copies the lambda).

[peah-webrtc, 2016/10/28 12:36:12]

You are right! I tried both locally and removed the wrong one.
I changed to the FunctionView instead.

Thanks for checking!!!! 

+    rtc::CritScope cs_render(&crit_render_);
+    rtc::CritScope cs_capture(&crit_capture_);
+    mutator(&config_);
+    ApplyConfig(config_);
+  }
+
+  AudioProcessing::Config GetConfig() const {
+    rtc::CritScope cs_render(&crit_render_);
+    rtc::CritScope cs_capture(&crit_capture_);
+    return config_;
+  }
+
  protected:
   // Overridden in a mock.
   virtual int InitializeLocked()
@@ -143,6 +160,9 @@ class AudioProcessingImpl : public AudioProcessing {
   struct ApmPublicSubmodules;
   struct ApmPrivateSubmodules;
 
+  // Submodule interface implementations.
+  std::unique_ptr<HighPassFilterImpl> high_pass_filter_impl_;

[the sun, 2016/10/28 10:52:53]

I don't see why you couldn't have a pointer to a HighPassFilter here instead,
provided you make the protected dtor of HighPassFilter public. Then you could
hide the entire impl in the .cc.

[peah-webrtc, 2016/10/28 12:19:52]

That is an awesome suggestion!!!
Done.

+
   class ApmSubmoduleStates {
    public:
     ApmSubmoduleStates();
@@ -234,6 +254,7 @@ class AudioProcessingImpl : public AudioProcessing {
   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()