Fix DisplayList update issue (#283)

Author: Kyle-Ye

Example/HostingExample/ViewController.swift

@@ -66,6 +66,6 @@ class ViewController: NSViewController {
 
 struct ContentView: View {
     var body: some View {
-        Color(uiColor: .red)
+        AppearanceActionModifierExample()
     }
 }

Sources/OpenSwiftUI/Integration/Hosting/UIKit/View/UIHostingView.swift

@@ -596,8 +596,14 @@ extension _UIHostingView: ViewRendererHost {
 
     package func requestUpdate(after: Double) {
         // TODO
+        requestImmediateUpdate()
     }
-    
+
+    func requestImmediateUpdate() {
+        // FIXME
+        setNeedsLayout()
+    }
+
     package func outputsDidChange(outputs: ViewGraph.Outputs) {
         // TODO
     }
@@ -609,11 +615,7 @@ extension _UIHostingView: ViewRendererHost {
     package func rootTransform() -> ViewTransform {
         preconditionFailure("TODO")
     }
-    
-    public func graphDidChange() {
-        // TODO
-    }
-    
+
     public func preferencesDidChange() {
         // TODO
     }