Return the current theme. Equivalent to the payload a napplet's theme.get would receive.
Register this with the runtime via runtime.registerService('theme', handler).
Publish a theme-change to the shell adapter. Updates the service's
internal current theme, invokes options.onBroadcast with a
theme.changed envelope, and returns the envelope.
The new theme payload
A theme.changed envelope (same one passed to onBroadcast)
A theme service bundle — the ServiceHandler that handles
theme.*envelopes, the host-facingpublishTheme(theme)handle for theme-change broadcasts, and agetCurrentTheme()accessor for host-side reads.