Added a protobuf field for the audio processing module to store the status of temporary experimental features that
are active in the module and its submodules.

BUG=webrtc:5778, webrtc:5777

Review URL: https://codereview.webrtc.org/1886233003

Cr-Commit-Position: refs/heads/master@{#12371}
diff --git a/webrtc/modules/audio_processing/audio_processing_impl.cc b/webrtc/modules/audio_processing/audio_processing_impl.cc
index a65598c..3a83d1c 100644
--- a/webrtc/modules/audio_processing/audio_processing_impl.cc
+++ b/webrtc/modules/audio_processing/audio_processing_impl.cc
@@ -1439,6 +1439,12 @@
   config.set_transient_suppression_enabled(
       capture_.transient_suppressor_enabled);
 
+  std::string experiments_description =
+      public_submodules_->echo_cancellation->GetExperimentsDescription();
+  // TODO(peah): Add semicolon-separated concatenations of experiment
+  // descriptions for other submodules.
+  config.set_experiments_description(experiments_description);
+
   std::string serialized_config = config.SerializeAsString();
   if (!forced &&
       debug_dump_.capture.last_serialized_config == serialized_config) {