Remove FileError interface

FileError was removed from File API [1] after Chrome had shipped the
functionality. Other browsers do not use it, returning a DOMError
instead. Using the `code` property has been logging deprecation
warnings since August 2013. The affected APIs will now yield
DOMExceptions instead (as DOMError is being removed from the platform
[2]). Script should inspect the `name` and `message` properties of the
error objects.

This affects:
* FileReader.error
* FileWriter.error
* FileSystem async API: passed to ErrorCallback on failure
* FileSystem sync API: thrown on failure

Intent: https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/kJMa2rpAYqI
Dashboard: https://www.chromestatus.com/feature/6687420359639040

[1] https://w3c.github.io/FileAPI/
[2] https://dom.spec.whatwg.org/#domerror

BUG=496901
R=foolip@chromium.org

Review-Url: https://codereview.chromium.org/2040563002
Cr-Commit-Position: refs/heads/master@{#406169}
50 files changed