Checks if data content for the given pyramid tile exists.
The given pyramid tile coordinates are always valid.
If an I/O error has occurred while checking.
this pyramid matches the given clear flags in.
This method checks the following clear flags:
The full pyramid size.
This is the size of the bottom-most pyramid level, given in tile pixels.
The event object of IPyramidBase.OnUpdated.
Logarithm of base two of tileSize.