I was wondering if WebGL is considered stable enough to be enabled by default. It makes some PDFs render much faster and it has been off by default for a while now, so we have had quite some time to test it.

If we decide to enable WebGL by default, we should not forget to update https://github.com/mozilla/pdf.js/blob/master/extensions/chromium/preferences_schema.json#L39 as well.

/cc @yurydelendik 
/cc @Snuffleupagus (because IIRC you were testing WebGL too)

const maxSize = Math.max(MAX_PATTERN_SIZE, realOutputSize);
      let size = Math.ceil(step * scale);
      if (size >= maxSize) {
        size = maxSize;
      } else {
        scale = size / step;
      }
      return { scale, size };
    },
    clipBbox: function clipBbox(graphics, bbox, x0, y0, x1, y1) {
      if (Array.isArray(bbox) && bbox.length === 4) {
        const bboxWidth = x1 - x0;
        const bboxHeight = y1 - y0;
        graphics.ctx.rect(x0, y0, bboxWidth, bboxHeight);
        graphics.clip();
        graphics.endPath();
      }
    },
    setFillAndStrokeStyleToContext: function setFillAndStrokeStyleToContext(
      graphics,
      paintType,
      color
    ) {
      const context = graphics.ctx,
        current = graphics.current;
      switch (paintType) {
        case PaintType.COLORED:
          const ctx = this.ctx;