Use virtual destructors

It turns out to be just a comment, as all except AudioMixer are RefBase.

There are only a few performance-sensitive cases where it's worth thinking
about whether you need a virtual destructor, and the headache usually
outweighs the benefit.

Change-Id: I716292f9556ec17c29ce8c76ac8ae602cb496533
diff --git a/services/audioflinger/AudioResamplerSinc.h b/services/audioflinger/AudioResamplerSinc.h
index 0e1bc44..f0a07b8 100644
--- a/services/audioflinger/AudioResamplerSinc.h
+++ b/services/audioflinger/AudioResamplerSinc.h
@@ -31,7 +31,7 @@
 public:
     AudioResamplerSinc(int bitDepth, int inChannelCount, int32_t sampleRate);
 
-    ~AudioResamplerSinc();
+    virtual ~AudioResamplerSinc();
 
     virtual void resample(int32_t* out, size_t outFrameCount,
             AudioBufferProvider* provider);