Move utility functions for sample rate to AudioUtilities.

Source/platform/audio/HRTFPanner.h

Index: Source/platform/audio/HRTFPanner.h
diff --git a/Source/platform/audio/HRTFPanner.h b/Source/platform/audio/HRTFPanner.h
index 4c5bf5482a5223f9975291a0ad06143c1976e717..594ea5848fc34618d826c06fd70399247ccfafb0 100644
--- a/Source/platform/audio/HRTFPanner.h
+++ b/Source/platform/audio/HRTFPanner.h
@@ -26,6 +26,7 @@
 #define HRTFPanner_h
 
 #include "platform/audio/AudioDelayDSPKernel.h"
+#include "platform/audio/AudioUtilities.h"
 #include "platform/audio/FFTConvolver.h"
 #include "platform/audio/HRTFDatabaseLoader.h"
 #include "platform/audio/Panner.h"
@@ -41,8 +42,7 @@ public:
     virtual void pan(double azimuth, double elevation, const AudioBus* inputBus, AudioBus* outputBus, size_t framesToProcess) OVERRIDE;
     virtual void reset() OVERRIDE;
 
-    size_t fftSize() const { return fftSizeForSampleRate(m_sampleRate); }
-    static size_t fftSizeForSampleRate(float sampleRate);
+    size_t fftSize() const { return AudioUtilities::fftSizeForSampleRate(m_sampleRate); }
 
     float sampleRate() const { return m_sampleRate; }