//       want to reference local types.
// This class keeps xaml file path and whether it is localizable.
// Serialize the instance to a string so that it can saved into a cache file.
// Create instance from a cache text string.
// cachInfo string must follow pattern like Localizable + FilePath.
// Localizable contains one character.
// Detect whether the local cache file exists or not.
// Clean up the state file.
// Save the local reference related information  from MarkupCompilePass1 task to cache file.
// Transfer the cache related information from mcPass1 to this instance.
// Save the cache information to the cache file.
// since TaskFileService.WriteFile adds it.
// Write InternalTypeHelperFile only when Pass1 asks Pass2 to do further check.
// Write the ApplicationFile for Pass2 compilation.
// to the corresponding data fields in this class.
// The first line must be for InternalTypeHelperFile.
// The second line is for Local Application Defintion file.
// For Library, the second line is an empty line.
// InternalTypeHelper code file path on the fly.
// The real file path would be passed from Pass1 task to Pass2 through the cache file.
// Pass2 then adds it to the appropriate output Item, otherwise, Pass2 just deletes this file.
// no further check is required in Pass2.