getPodArgsBuffer(nbytes) {
	        let buffer = undefined;
	        if (this.podArgStagingBuffers.length >= this.maxNumPodArgsStagingBuffers) {
	            buffer = this.podArgStagingBuffers.shift();
	        }
	        // minimum of 16 bytes
	        let allocSize = 16;
	        if (buffer !== undefined) {
	            allocSize = buffer.size;
	            if (buffer.size < nbytes) {
	                buffer.destroy();
	                buffer = undefined;
	            }
	        }
	        while (allocSize < nbytes) {
	            allocSize *= 2;
	        }
	        if (buffer == undefined) {
	            // create uniform buffer
	            buffer = this.device.createBuffer({
	                size: allocSize,
	                usage: GPUBufferUsage.UNIFORM | GPUBufferUsage.COPY_DST,
	            });
	        }
	        support.assert(nbytes <= buffer.size);
	        return buffer;
	    }
Get the pod arg staging buffer
\param nbytes The minimum size.
\return The allocated buffer