as this code has been reconsolidated in the base class for
all to use. For everyone, if the mime type is unknown or octet,
then try to guess a content type by file extension in doContent.
Also, if we can't find a mime type, create a new one for all platforms
so we don't need to bring up the ucth dialog.
sr=sspitzer
code review will come when this is done and gets turned on.
Mac specific implementation of the helper app service. Note: this is incomplete...I have added FIX ME comments
in all the places where we need Mac specific information for interacting with internet config.
