The BroadcastChannel API shipping Chrome 54 (https://developers.google.com/web/updates/2016/09/broadcastchannel?hl=en)

Currently, an inactive service worker does not wake up if you send a message to it via a broadcast channel. This seems limiting and makes the BC API less useful. Sharing the same channel across multiple contexts is one of its benefits.

It's also worth noting that `navigator.serviceWorker.controller.postMessage()` will wake up the service worker. It would be nice to support the BC API in service workers so both scenarios are consistent.