Fix a test failure when IP Permission check is turned on

chrome/browser/media/chrome_webrtc_audio_quality_browsertest.cc

Index: chrome/browser/media/chrome_webrtc_audio_quality_browsertest.cc
diff --git a/chrome/browser/media/chrome_webrtc_audio_quality_browsertest.cc b/chrome/browser/media/chrome_webrtc_audio_quality_browsertest.cc
index 45debc951ed22919e7d69dd1d57c8df728327268..a85d55606fc705b5d840c12aeaa7b208faf974a4 100644
--- a/chrome/browser/media/chrome_webrtc_audio_quality_browsertest.cc
+++ b/chrome/browser/media/chrome_webrtc_audio_quality_browsertest.cc
@@ -137,6 +137,9 @@ class MAYBE_WebRtcAudioQualityBrowserTest : public WebRtcTestBase {
     // getUserMedia, and the getUserMedia-based tests will play back a file
     // through the fake device using using --use-file-for-fake-audio-capture.
     command_line->AppendSwitch(switches::kUseFakeDeviceForMediaStream);
+
+    // Add loopback interface such that there is always connectivity.
+    command_line->AppendSwitch(switches::kAllowLoopbackInPeerConnection);
   }
 
   void ConfigureFakeDeviceToPlayFile(const base::FilePath& wav_file_path) {