As V8 becomes more and more spec-compliant, Promise polyfill libraries
like core.js expect fully correct. However, our Promises do not yet
support Symbol.species. Therefore, a case like
```
var test = new Promise(function(){});
test.constructor = function(){};
Promise.resolve(test)
```
would lead to an unhandled Promise rejection, whereas it should not
because test.constructor[Symbol.species] is undefined, so test.then
should end up constructing %Promise% as a fallback, rather than
calling test.constructor as if it were a constructor, which leads
this error checking code to throw.
For now, this patch removes the error checking code (which was not
present until recently). In an interactive test using core.js, the
error message on the console goes away with this patch. When @@species
support is in place, this patch can be reverted. A regression test
is added which checks for the same thing.
Partially reverted patch was originally out for review at
https://codereview.chromium.org/1531073004
BUG=v8:4633
LOG=Y
R=adamk,caitp88@gmail.com
Review URL: https://codereview.chromium.org/1578893002
Cr-Commit-Position: refs/heads/master@{#33217}
ee9d7acafc