Adds detection of audio glitches for playout on iOS (reland)

Second attempt to land https://chromium-review.googlesource.com/c/522563/

TBR: minyue
Bug: b/38018041
Change-Id: I938f4a490b6357cd1ac7b34fe445215a746fab43
Reviewed-on: https://chromium-review.googlesource.com/533214
Commit-Queue: Henrik Andreasson <henrika@webrtc.org>
Reviewed-by: Minyue Li <minyue@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#18572}
diff --git a/webrtc/webrtc.gni b/webrtc/webrtc.gni
index d4acaf5..676ab2f 100644
--- a/webrtc/webrtc.gni
+++ b/webrtc/webrtc.gni
@@ -147,6 +147,12 @@
   # use file-based audio playout and record.
   rtc_use_dummy_audio_file_devices = false
 
+  # When set to true, replace the audio output with a sinus tone at 440Hz.
+  # The ADM will ask for audio data from WebRTC but instead of reading real
+  # audio samples from NetEQ, a sinus tone will be generated and replace the
+  # real audio samples.
+  rtc_audio_device_plays_sinus_tone = false
+
   # When set to true, test targets will declare the files needed to run memcheck
   # as data dependencies. This is to enable memcheck execution on swarming bots.
   rtc_use_memcheck = false