In the following spots a "MouseUp" eventName is being used, which does look inconsistent considering that the "Mouse Down"/"Mouse Enter"/"Mouse Exit" eventNames all have a space in them.
Is this inconsistency actually expected, or is it a simple typo? If the former, then a comment explaining *why* would be appropriate; otherwise we should just fix this :-)

 - https://github.com/mozilla/pdf.js/blob/25b84ce84c95ba06d1ee57e578672048269c39c1/src/display/annotation_layer.js#L806

 - https://github.com/mozilla/pdf.js/blob/25b84ce84c95ba06d1ee57e578672048269c39c1/src/display/annotation_layer.js#L945

 - https://github.com/mozilla/pdf.js/blob/25b84ce84c95ba06d1ee57e578672048269c39c1/src/display/annotation_layer.js#L1034

 - https://github.com/mozilla/pdf.js/blob/25b84ce84c95ba06d1ee57e578672048269c39c1/src/display/annotation_layer.js#L1168

/cc @calixteman 
showSpacedText: 45,
  nextLineShowText: 46,
  nextLineSetSpacingShowText: 47,
  setCharWidth: 48,
  setCharWidthAndBounds: 49,
  setStrokeColorSpace: 50,
  setFillColorSpace: 51,
  setStrokeColor: 52,
  setStrokeColorN: 53,
  setFillColor: 54,
  setFillColorN: 55,
  setStrokeGray: 56,
  setFillGray: 57,
  setStrokeRGBColor: 58,
  setFillRGBColor: 59,
  setStrokeCMYKColor: 60,
  setFillCMYKColor: 61,
  shadingFill: 62,
  beginInlineImage: 63,
  beginImageData: 64,
  endInlineImage: 65,
  paintXObject: 66,
  markPoint: 67,
  markPointProps: 68,
  beginMarkedContent: 69,
  beginMarkedContentProps: 70,
  endMarkedContent: 71,
  beginCompat: 72,
  endCompat: 73,
  paintFormXObjectBegin: 74,