nsDrawingSurfaceMac::IsOffscreen bug???

[Shai Spharim]

The function nsDrawingSurfaceMac::IsOffscreen is declared and defined in 
nsDrawingSurfaceMac.h as:

NS_IMETHOD IsOffscreen(PRBool *aOffScreen) {return mIsOffscreen;}

This looks like a mistake, and is different from the other OS's 
nsDrawingSurfaceXYZ::IsOffscreen. *aOffScreen isn't being modified
This looks like the proper implemantation:

NS_IMETHOD nsDrawingSurfaceMac::IsOffscreen(PRBool *aOffScreen)
{
  *aOffScreen = mIsOffscreen;
  return NS_OK;
}

What gives?