[start.sharedworker.html]
  [underlying sink's write should not be called until start finishes]
    expected: FAIL

  [underlying sink's close should not be called until start finishes]
    expected: FAIL

  [underlying sink's write or close should not be called if start throws]
    expected: FAIL

  [underlying sink's write or close should not be invoked if the promise returned by start is rejected]
    expected: FAIL

  [returning a thenable from start() should work]
    expected: FAIL

  [controller.error() during start should cause writes to fail]
    expected: FAIL

  [controller.error() during async start should cause existing writes to fail]
    expected: FAIL

  [when start() rejects, writer promises should reject in standard order]
    expected: FAIL