Remove audio playout generator from APM API

This API is and has always been unused.

Bug: webrtc:5298
Change-Id: If1201d37a00e387567d44a9ed8be99a157915b47
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/174661
Reviewed-by: Per Ã…hgren <peah@webrtc.org>
Commit-Queue: Sam Zackrisson <saza@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31180}
diff --git a/modules/audio_processing/include/audio_processing.h b/modules/audio_processing/include/audio_processing.h
index 5f90d7d..25b08c6 100644
--- a/modules/audio_processing/include/audio_processing.h
+++ b/modules/audio_processing/include/audio_processing.h
@@ -24,10 +24,10 @@
 #include <vector>
 
 #include "absl/types/optional.h"
+#include "api/array_view.h"
 #include "api/audio/echo_canceller3_config.h"
 #include "api/audio/echo_control.h"
 #include "api/scoped_refptr.h"
-#include "modules/audio_processing/include/audio_generator.h"
 #include "modules/audio_processing/include/audio_processing_statistics.h"
 #include "modules/audio_processing/include/config.h"
 #include "rtc_base/arraysize.h"
@@ -614,16 +614,6 @@
   // all pending logging tasks are completed.
   virtual void DetachAecDump() = 0;
 
-  // Attaches provided webrtc::AudioGenerator for modifying playout audio.
-  // Calling this method when another AudioGenerator is attached replaces the
-  // active AudioGenerator with a new one.
-  virtual void AttachPlayoutAudioGenerator(
-      std::unique_ptr<AudioGenerator> audio_generator) = 0;
-
-  // If no AudioGenerator is attached, this has no effect. If an AecDump is
-  // attached, its destructor is called.
-  virtual void DetachPlayoutAudioGenerator() = 0;
-
   // Get audio processing statistics.
   virtual AudioProcessingStats GetStatistics() = 0;
   // TODO(webrtc:5298) Deprecated variant. The |has_remote_tracks| argument