Multiple overlapping activities require proximity monitoring (namely,
CallViewController and listening to audio messages).
These activities can overlap arbitrarily, so we use a reference counting
strategy to keep proximity monitoring on as long as one of these activities is
active.
- Prefer checking `.isEmpty` rather than `.count == 0` for Swift collections (can be more optimal)
- Avoid comparing `BOOL` explicitly to `NO` (considered bad practice since `BOOL` is a `signed char`)
- Specify unused `SGX_FLAGS` as `__unused` to silence warnings
- sync speakerphone state manipulated from system call screen
- Revert audio session after call failure, ensures media plays out of
speaker after placing a failing call.
- Replace notification with delegate pattern since we're already using
delegate pattern here.
- Fixes voiceover accessibility after voice memo
- Avoid audio blip after pressing hangup
- Rename CallAudioSession -> OWSAudioSession
Going to start using it for other non-call things since we want to
gather all our audio session concerns.
- Resume background audio when done playing video
- Extract OWSVideoPlayer which ensures audio is in proper state before
playback
- Move recording session logic to shared OWSAudioSession
- Deactivate audio session when complete
// FREEBIE
