Define integration with the Page Lifecycle API

[reillyeon]

In order for usage of the Web Serial API to not prevent a site from being included in features such as Chromium's BFCache this API needs to define how it integrates with the Page Lifecycle API. Some questions:

• Should serial port's be automatically closed when the page becomes frozen? (Probably yes.)
• If so, how should that be communicated to the page via the SerialPort interface and its readable and writable streams?
• How should connect and disconnect events that occur while the page is frozen be handled? Options,
  1. Queue all events until the page is resumed?
  2. Coalesce events for a single device so that only the effective change (if any) since the page was frozen is communicated on resume?
  3. Discard all events and ask developers to call getPorts() on resume?