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

PASS: Creating SharedWorker with different URLs but the same name
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