Often WebKit allows the client to decide the policy for certain operations. For instance, a client may want to open a link in a new tab,
block a navigation entirely, query the user or trigger a download instead of a navigation. In these cases WebKit will fire the
decide_policy signal with a PolicyDecision
object. If the signal handler does nothing, WebKit will act as if use
was called as soon as signal handling completes. To make a policy decision asynchronously, simply increment the reference count of the
PolicyDecision object.