This fixes the following bugs:
* `BroadcastReceiver` was never being created due to incorrect guard
condition `if (pollForUpdatesReceiver != null)` (should have been
`== null`).
* Called `unregisterReceiver` rather than `registerReceiver`.
* Even if it did work, it didn't make an effort to unregister the receiver.
In addition, the creation and listening with the `BroadcastReceiver is
now done in a way similar to the other swap views:
* Create it as a `final` member variable.
* `registerReceiver` when view is inflated.
* `unregisterReceiver` when view is detached.
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