fix(blob, file, tests): Minor improvements for Blob and File implementations

[octet-stream]

The purpose of this PR is:

This PR includes minor improvements and fixes for File and Blob internals

This is what had to change:

• Blob.stream().cancel() triggers iterator.return() on underlying source;
• Improve type casting for FilePropertyBag.lastModified to match browsers behaviour (This behaviour tested in Chrome, Firefox and Safari), now NaN values will be interpreted as 0 rather than Date.now();
• Improve errors reported by Blob constructor;
• Move Blob.slice() implementation outside the Blob class and implement it as generator function. Since blob treats iterable objects as a sequence and behaviour looks the same;
• Apply private values as we iterate over blob parts.

This is what like reviewers to know:

This PR is more of a housekeeping with minor changes only. This also changes one thing in terms of File behaviour, just to match File implementations in browsers.

---

• I prefixed the PR-title with docs: , fix(area): , feat(area): or breaking(area):
• I updated ./CHANGELOG.md with a link to this PR or Issue
• I updated the README.md
• I Added unit test(s)

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[octet-stream]

Ah, same error for blobs and files backed by fs. Maybe you just run tests with -s flag? I think this should fix this errors :)

[octet-stream]

@jimmywarting @LinusU can somebody review this one, please?

[jimmywarting]

also could you test npm run test-wpt manualy also, there is no CI job for it yet...

[octet-stream]

also could you test npm run test-wpt manualy also, there is no CI job for it yet...

That's what I do locally :)