`SilentAudioGenerator` could output a fractional audio frame, and this could cause downstream components to throw because of trying to read a complete audio frame but only seeing a partial one.
Calculate the output buffer size based on the frame size (which is a no-op for stereo 16-bit audio) and calculate a total number of frames to output then multiple by the frame size.
PiperOrigin-RevId: 494992941
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