Enable new getUserMedia audio constraints algorithm behind a flag.

content/public/common/content_features.cc

Index: content/public/common/content_features.cc
diff --git a/content/public/common/content_features.cc b/content/public/common/content_features.cc
index 15fb85f6ab5ca9ed4a15758c954097dfafcf506a..59d38ce7b75fa325fb7bf363997c64d9381b1ecf 100644
--- a/content/public/common/content_features.cc
+++ b/content/public/common/content_features.cc
@@ -136,6 +136,10 @@ const base::Feature kMediaDocumentDownloadButton{
     base::FEATURE_DISABLED_BY_DEFAULT
 };
 
+// Enables the old algorithm for processing audio constraints in getUserMedia().
+const base::Feature kMediaStreamOldAudioConstraints{
+    "MediaStreamOldAudioConstraints", base::FEATURE_ENABLED_BY_DEFAULT};
+
 // Enables the old algorithm for processing video constraints in getUserMedia().
 const base::Feature kMediaStreamOldVideoConstraints{
     "MediaStreamOldVideoConstraints", base::FEATURE_DISABLED_BY_DEFAULT};