Move utility functions for sample rate to AudioUtilities.

Source/platform/audio/AudioUtilities.h

 /*
  * Copyright (C) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 24 matching lines @@
 PLATFORM_EXPORT float decibelsToLinear(float);
 
 // timeConstant is the time it takes a first-order linear time-invariant system
 // to reach the value 1 - 1/e (around 63.2%) given a step input response.
 // discreteTimeConstantForSampleRate() will return the discrete time-constant for the specific sampleRate.
 PLATFORM_EXPORT double discreteTimeConstantForSampleRate(double timeConstant, double sampleRate);
 
 // Convert the time to a sample frame at the given sample rate.
 PLATFORM_EXPORT size_t timeToSampleFrame(double time, double sampleRate);
 
+// Check that |sampleRate| is a valid rate for AudioBuffers.
+PLATFORM_EXPORT bool isValidAudioBufferSampleRate(float sampleRate);
+
+// Return max/min sample rate supported by AudioBuffers.
+PLATFORM_EXPORT float minAudioBufferSampleRate();
+PLATFORM_EXPORT float maxAudioBufferSampleRate();
 } // AudioUtilites
 } // namespace blink
 
 #endif // AudioUtilities_h