WebRTC hybrid Agc experiment.

This CL adds flags and Finch features for a new WebRTC
feature. It also applies the flag settings to WebRTC Audio Processing.

Bug: chromium:873650 webrtc:7494
Change-Id: If2062aaf4f8bf48e26742b2841187f02221141ff
Reviewed-on: https://chromium-review.googlesource.com/1172438
Commit-Queue: Alex Loiko <[email protected]>
Reviewed-by: Alex Moshchuk <[email protected]>
Reviewed-by: Guido Urdaneta <[email protected]>
Cr-Commit-Position: refs/heads/master@{#582880}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index 8d53af6..7914d2a 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -1240,6 +1240,9 @@
 extern const char kWebrtcEchoCanceller3Name[];
 extern const char kWebrtcEchoCanceller3Description[];
 
+extern const char kWebrtcHybridAgcName[];
+extern const char kWebrtcHybridAgcDescription[];
+
 extern const char kWebrtcHwDecodingName[];
 extern const char kWebrtcHwDecodingDescription[];