Test that EventSource tries to reconnect if there's no server response when making cross-origin requests.

On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".

PASS es = new EventSource("http://127.0.0.1:12345/event-stream") did not throw exception.
PASS got error event and readyState is CONNECTING
PASS es = new EventSource("http://localhost:54321/event-stream") did not throw exception.
PASS got error event and readyState is CONNECTING
PASS successfullyParsed is true

TEST COMPLETE