Add support for audio input mute detection on all platforms

media/audio/virtual_audio_input_stream.cc

Index: media/audio/virtual_audio_input_stream.cc
diff --git a/media/audio/virtual_audio_input_stream.cc b/media/audio/virtual_audio_input_stream.cc
index c832a8298346da98970b99d80def6399a63b2509..6d1189ee99501251bc39e0dcf2c3555c9629453c 100644
--- a/media/audio/virtual_audio_input_stream.cc
+++ b/media/audio/virtual_audio_input_stream.cc
@@ -173,4 +173,8 @@ bool VirtualAudioInputStream::GetAutomaticGainControl() {
   return false;
 }
 
+bool VirtualAudioInputStream::IsMuted() {
+  return false;
+}
+
 }  // namespace media