measureText(renderer, text = this._text) {
		return this.metrics.measureText(text, this.canvasTexture.context);
	}
measure the given text size in pixels
@param {CanvasRenderer|WebGLRenderer} renderer - reference to the active renderer
@param {string} [text] - the text to be measured
@returns {TextMetrics} a TextMetrics object defining the dimensions of the given piece of text