[Cocoa] Modernize one-method authentication
https://bugs.webkit.org/show_bug.cgi?id=134051

Reviewed by Anders Carlsson.

Instead of an NSURLConnection-style delegate method that takes a challenge and responds to
its sender, provide an NSURLSession-style method that takes a challenge and a completion
handler.

* UIProcess/API/Cocoa/WKNavigationDelegatePrivate.h: Declared new delegate method, replacing
old unused method.
* UIProcess/Cocoa/NavigationState.h: Renamed flag in m_navigationDelegateMethods struct.
* UIProcess/Cocoa/NavigationState.mm:
(WebKit::NavigationState::setNavigationDelegate): Check for new delegate method and update
new flag.

(WebKit::NavigationState::LoaderClient::canAuthenticateAgainstProtectionSpaceInFrame): If
the delegate implements the new method, return true (if it cannot handle the protection
space, it can reject it through the completion handler), except for server-trust
authentication, which is not supported yet.
(WebKit::NavigationState::LoaderClient::didReceiveAuthenticationChallengeInFrame): If the
delegate implements the new method, call it, passing a completion handler that calls the
right AuthenticationDecisionListener function based on its disposition and credential
parameters.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@170137 268f45cc-cd09-0410-ab3c-d52691b4dbfc