NativeFileSystem File API implementation is incomplete

[jasonsanjose]

The public APIs in NativeFileSystem should follow the following W3C specs drafts

http://www.w3.org/TR/2011/WD-FileAPI-20111020/
http://www.w3.org/TR/2011/WD-file-writer-api-20110419/
http://www.w3.org/TR/2011/WD-file-system-api-20110419/
http://www.w3.org/TR/progress-events/

Our approach to implementation has been on an as-needed basis. Features like non-text file reading, progress events, synchronous APIs, etc. are not yet required or may never be implemented.

This issue is for tracking TODOs in NativeFileSystem.

[njx]

QRB reviewed. Marking "to user story"--we might want to flesh this out for extensibility. (We'll also add implementations as we need them to support feature work.)

[jlondon]

Added to backlog - closing