[TTWF Shanghai] Added idlharness test for FileAPI
Update FileAPI IDL to latest editor's draft
Update idlharness tests to reflect #388 cleanup
Split up the FileAPI idlharness test case in a manual and an autoomated part.
Remove trailing whitespace from the FileAPI interfaces tests.
Adding WebDriver Modal tests

Signed-off-by: AutomatedTester <dburns@mozilla.com>

blah
Merge pull request #583 from w3c/pr/289

FileAPI interface test