Test simple shared worker sharing cases. Should print several PASS lines followed by DONE.

PASS: Exception thrown when creating SharedWorker with different URLs but same name: URLMismatchError: Failed to construct 'SharedWorker': The location of the SharedWorker named 'name' does not exactly match the provided URL ('some-other-url.js').
PASS: Accessing new instance of shared worker: self.foo: undefined
PASS: Setting global variable in shared worker: self.foo = 1234: 1234
PASS: Accessing simultaneously-loaded instance of shared worker: self.foo: 1234
PASS: Accessing new instance of shared worker: self.foo: undefined
PASS: Accessing already-loaded instance of shared worker: self.foo: 1234
DONE