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)

if (currentGL) {
      return;
    }
    
    currentCanvas = document.createElement("canvas");
    currentGL = currentCanvas.getContext("webgl", {
      premultipliedalpha: false,
    });
  }
  const smaskVertexShaderCode =
    "\
  attribute vec2 a_position;                                    \
  attribute vec2 a_texCoord;                                    \
                                                                \
  uniform vec2 u_resolution;                                    \
                                                                \
  varying vec2 v_texCoord;                                      \
                                                                \
  void main() {                                                 \
    vec2 clipSpace = (a_position / u_resolution) * 2.0 - 1.0;   \
    gl_Position = vec4(clipSpace * vec2(1, -1), 0, 1);          \
                                                                \
    v_texCoord = a_texCoord;                                    \
  }                                                             ";
  const smaskFragmentShaderCode =