nsIFontPackageProxy in Firefox 1.5

 Request a font package. The proxy will call font package 
 handler to download the font package
 @param aFontPackID a font package ID.
 The id have the following naming convenation 
  name_space:name
 we currently define one name space
    lang - a font package for a particular language group
 and udnder the lang name space, we use the language code to identify
 the package, below are the defined packages
   ja - Japanese font package ("lang:ja")
   ko - Korean font package ("lang:ko")
   zh-TW - Traditional Chinese font package ("lang:zh-TW")
   zh-CN - Simplified Chinese font package ("lang:zh-CN")
 In the future, we may want to add
    ar - Arabic font packges ("lang:ar")
    he - Hebrew font packages ("lang:he")
    th - Thai font package ("lang:th")
 other name space are reserved for now.

 This interface is implemented by Gecko for internal purpose
 It is a service and are different from nsIFontPackageHandler although
 the method signature is the same. 
 Embedding application should not see this interface.