AudioTrack::mute() is unused so remove it

If ever needed again, it could be implemented on client side by forcing
a track volume of 0.

Change-Id: I88a9b4f675b6dca2948549414f9ec2c192d29269
diff --git a/media/libmedia/IAudioTrack.cpp b/media/libmedia/IAudioTrack.cpp
index 867d1a5..e92f8aa 100644
--- a/media/libmedia/IAudioTrack.cpp
+++ b/media/libmedia/IAudioTrack.cpp
@@ -33,7 +33,7 @@
     START,
     STOP,
     FLUSH,
-    MUTE,
+    RESERVED, // was MUTE
     PAUSE,
     ATTACH_AUX_EFFECT,
     ALLOCATE_TIMED_BUFFER,
@@ -88,14 +88,6 @@
         remote()->transact(FLUSH, data, &reply);
     }
 
-    virtual void mute(bool e)
-    {
-        Parcel data, reply;
-        data.writeInterfaceToken(IAudioTrack::getInterfaceDescriptor());
-        data.writeInt32(e);
-        remote()->transact(MUTE, data, &reply);
-    }
-
     virtual void pause()
     {
         Parcel data, reply;
@@ -192,11 +184,6 @@
             flush();
             return NO_ERROR;
         } break;
-        case MUTE: {
-            CHECK_INTERFACE(IAudioTrack, data, reply);
-            mute( data.readInt32() );
-            return NO_ERROR;
-        } break;
         case PAUSE: {
             CHECK_INTERFACE(IAudioTrack, data, reply);
             pause();