Add support for audio input mute detection on all platforms

media/audio/audio_io.h

Index: media/audio/audio_io.h
diff --git a/media/audio/audio_io.h b/media/audio/audio_io.h
index 105e32eb362b7dd8caccd40bc8037f74705ddf40..3add053952c5334927cbdfe622433c37fd018bc4 100644
--- a/media/audio/audio_io.h
+++ b/media/audio/audio_io.h
@@ -164,6 +164,9 @@ class MEDIA_EXPORT AudioInputStream {
 
   // Returns the Automatic Gain Control (AGC) state.
   virtual bool GetAutomaticGainControl() = 0;
+
+  // Returns the current muting state for the microphone.
+  virtual bool IsMuted() = 0;
 };
 
 }  // namespace media