Event is not triggered when Promise resolver throws

[l1bbcsg]

Steps to reproduce

Run polyfill in environment that natively supports unhandledrejection event (tested in Chrome 65).

Sample code

window.addEventListener('unhandledrejection', (e) => {
	if (e instanceof PromiseRejectionEvent) {
		console.log('native unhandledrejection', e.reason)
	} else {
		console.log('polyfilled unhandledrejection', e.reason)
	}
});
polyfill(); // force polyfill

// A
new Promise((resolve, reject) => reject('simple reject'));

// B
Promise.reject('static reject');

// C
new Promise((resolve, reject) => {
	throw new Error('throw');
});

Expected results

Both native and polyfill events fire consistently.

Actual results

Native unhandledrejection fires in all three cases.
Polyfilled unhandledrejection fires in cases A and B, but not C.