Move utility functions for sample rate to AudioUtilities.

Source/platform/audio/AudioUtilities.h

Index: Source/platform/audio/AudioUtilities.h
diff --git a/Source/platform/audio/AudioUtilities.h b/Source/platform/audio/AudioUtilities.h
index a7e02d721f2435224c4081f2ff9c4f8a9b55992c..1fd287a7fdbb6a599975892a84cb707eab57d41f 100644
--- a/Source/platform/audio/AudioUtilities.h
+++ b/Source/platform/audio/AudioUtilities.h
@@ -42,6 +42,12 @@ PLATFORM_EXPORT double discreteTimeConstantForSampleRate(double timeConstant, do
 // 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