provide isError and use it in place of instanceof Error

[graingert]

I'm submitting a ...

• bug report
• feature request
• other (Please do not submit support requests here (see above))

Current behavior:

angular sometimes stringifies unhandled rejections, even if they're errors.

Expected / new behavior:

Angular should pass them on to the correct excetion handler

Minimal reproduction of the problem with instructions:
Difficult to reproduce

Angular version: 1.x.y
1.6.3

Browser: [all | Chrome XX | Firefox XX | IE XX | Safari XX | Mobile Chrome XX | Android X.X Web Browser | iOS XX Safari | iOS XX UIWebView | iOS XX WKWebView ]
Chrome

Anything else:
Provide angular.isError:

function isError(V) {
  var tagName = Object.prototype.toString.call(V);
  return (
    tagName === '[object Error]' ||
    tagName === '[object Exception]' ||
    V instanceof Error
  );
}

MIT from https://github.com/yefremov/iserror/blob/master/index.js

and use it wherever instanceof Error was used.

[gkalpak]

I don't think it makes sense to complicate things unless there is a reproducible, valid usecase, which makes it worth it.

[graingert]

this is an error passed from another context, eg another frame, or webworker

[gkalpak]

OK, sounds reasonable. Any idea where object Exception comes from? (Also, what about DOMExceptions?)

[gkalpak]

Let's move the discussion to #15872.