Dumps the content of a window
@param aWindowToDump the window to dump (may be an iframe etc)
@param aFile the file to dump to. It will be created if necessary, otherwise
truncated. If nil, write to stdout.
@param aFlagsMask some flags that determine what to dump
@param aFlagsMask some flags that determine what to dump
@param aResult a status value indicating whether the dump happened,
whether the page was still loading, or whether some other error happened.
Compares the contents of frame model files
@param aBaseFile the baseline file, opened with read permissions
@param aVerFile file containing the results to verify, opened with read permissions
@param aFlags flags specifying output verbosity
@param aResult result of the comparison: zero if the files are same, non-zero if different