Bug 681192. Part 11: Don't snap scrollrange endpoints to device pixels anymore. r=matspal

  nsRect range = GetScrolledRect();

  range.width -= aWidth;

  range.height -= aHeight;

  nsPresContext* presContext = mOuter->PresContext();

  PRInt32 appUnitsPerDevPixel = presContext->AppUnitsPerDevPixel();

  range.width =

    AlignToDevPixelRoundingToZero(range.XMost(), appUnitsPerDevPixel) - range.x;

  range.height =

    AlignToDevPixelRoundingToZero(range.YMost(), appUnitsPerDevPixel) - range.y;

  range.x = AlignToDevPixelRoundingToZero(range.x, appUnitsPerDevPixel);

  range.y = AlignToDevPixelRoundingToZero(range.y, appUnitsPerDevPixel);

  return range;

}