https://github.com/mozilla/pdf.js/issues/6397#issuecomment-164954332 Would have been a lot easier to find had there been an assertion checking that string16 didn't go out of bounds of the 16bit number.

setLineJoin: 4,
  setMiterLimit: 5,
  setDash: 6,
  setRenderingIntent: 7,
  setFlatness: 8,
  setGState: 9,
  save: 10,
  restore: 11,
  transform: 12,
  moveTo: 13,
  lineTo: 14,
  curveTo: 15,
  curveTo2: 16,
  curveTo3: 17,
  closePath: 18,
  rectangle: 19,
  stroke: 20,
  closeStroke: 21,
  fill: 22,
  eoFill: 23,
  fillStroke: 24,
  eoFillStroke: 25,
  closeFillStroke: 26,
  closeEOFillStroke: 27,
  endPath: 28,
  clip: 29,
  eoClip: 30,
  beginText: 31,
  endText: 32,
  setCharSpacing: 33,