lib.es6.d.ts for file reader event is inaccurate

[AmitMY]

TypeScript Version: Latest

File lib.es6.d.ts.

Code

let reader = new FileReader();
reader.onload = e => fileObj.src = e.target.result;

Expected behavior:
Not an error

Actual behavior:

Unresolved variable 'result'

Description:

interface Event has target: EventTarget;
And
interface EventTarget does not have result

[mhegazy]

looks like the same root cause as #299.

[zhengbli]

Should be covered by microsoft/TypeScript-DOM-lib-generator#207