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)

return WebGLUtils.drawFigures(
      width,
      height,
      backgroundColor,
      figures,
      context
    );
  }
  clear() {
    WebGLUtils.cleanup();
  }
}
const WebGLUtils = (function WebGLUtilsClosure() {
  function loadShader(gl, code, shaderType) {
    const shader = gl.createShader(shaderType);
    gl.shaderSource(shader, code);
    gl.compileShader(shader);
    const compiled = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
    if (!compiled) {
      const errorMsg = gl.getShaderInfoLog(shader);
      throw new Error("Error during shader compilation: " + errorMsg);
    }
    return shader;
  }
  function createVertexShader(gl, code) {
    return loadShader(gl, code, gl.VERTEX_SHADER);
  }
  function createFragmentShader(gl, code) {