useProgram( program ) {

		if ( this.currentProgram !== program ) {

			this.gl.useProgram( program );

			this.currentProgram = program;

			return true;

		}

		return false;

	}
Defines the usage of the given WebGL program.

This method caches the state so `gl.useProgram()` is only
called when necessary.

@param {WebGLProgram} program - The WebGL program to use.
@return {boolean} Whether a program change has been executed or not.