Add HTML5 API Interfaces to Window

[oleersoy]

Attempting to define a check for HTML5 File API support in Angular like this:

private hasHtml5FileApiSupport;
  constructor(@Optional() @Inject(DOCUMENT) document: Document) {
    const w = document.defaultView;
    this.hasHtml5FileApiSupport = w.File && w.FileReader && w.FileList && w.Blob;

However VSCode draws red squigglies under File, FileReader, and FileList since there are not part of the Window interface. It would be nice if they were. We can still do NPE checks on them.

[oleersoy]

https://stackoverflow.com/questions/53292312/checking-for-html5-file-api-support-in-angular

https://stackoverflow.com/questions/53305340/typescript-html5-api-typings/53305917#53305917

[oleersoy]

Related Angular issue:
angular/angular#7341

[saschanaz]

Should probably be fixed by introducing the global type.

[jakebailey]

Just checking old issues; this one was fixed in #37464. Playground Link