[pigeon] Clean up legacy registrant code

packages/pigeon/example/README.md

@@ -439,8 +439,7 @@ Register the handler with the generated method.
 <?code-excerpt "ios/Runner/AppDelegate.swift (swift-init-event)"?>
 ```swift
 let eventListener = EventListener()
-StreamEventsStreamHandler.register(
-  with: controller.binaryMessenger, streamHandler: eventListener)
+StreamEventsStreamHandler.register(with: binaryMessenger, streamHandler: eventListener)
 ```
 
 ### Kotlin

packages/pigeon/example/app/ios/Runner/AppDelegate.swift

@@ -94,31 +94,16 @@ func sendEvents(_ eventListener: EventListener) {
 }
 
 @main
-@objc class AppDelegate: FlutterAppDelegate {
-  override func application(
-    _ application: UIApplication,
-    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
-  ) -> Bool {
-    GeneratedPluginRegistrant.register(with: self)
-    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
-  }
-}
-
-// TODO(stuartmorgan): Once 3.33+ reaches stable, remove this subclass and move the setup to
-// AppDelegate.register(...). This approach is only used because this example needs to support
-// both stable and master, and 3.32 doesn't have FlutterPluginRegistrant, while 3.33+ can't use
-// the older application(didFinishLaunchingWithOptions) approach.
-@objc class ExampleViewController: FlutterViewController {
-  override func awakeFromNib() {
-    super.awakeFromNib()
+@objc class AppDelegate: FlutterAppDelegate, FlutterImplicitEngineDelegate {
+  func didInitializeImplicitFlutterEngine(_ engineBridge: FlutterImplicitEngineBridge) {
+    GeneratedPluginRegistrant.register(with: engineBridge.pluginRegistry)
 
     let api = PigeonApiImplementation()
+    let binaryMessenger = engineBridge.applicationRegistrar.messenger()
     ExampleHostApiSetup.setUp(binaryMessenger: binaryMessenger, api: api)
-    let controller = self
     // #docregion swift-init-event
     let eventListener = EventListener()
-    StreamEventsStreamHandler.register(
-      with: controller.binaryMessenger, streamHandler: eventListener)
+    StreamEventsStreamHandler.register(with: binaryMessenger, streamHandler: eventListener)
     // #enddocregion swift-init-event
     sendEvents(eventListener)
   }

packages/pigeon/example/app/ios/Runner/Base.lproj/Main.storyboard

@@ -7,10 +7,10 @@
         <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
     </dependencies>
     <scenes>
-        <!--Example View Controller-->
+        <!--Flutter View Controller-->
         <scene sceneID="tne-QT-ifu">
             <objects>
-                <viewController id="BYZ-38-t0r" customClass="ExampleViewController" customModule="Runner" customModuleProvider="target" sceneMemberID="viewController">
+                <viewController id="BYZ-38-t0r" customClass="FlutterViewController" sceneMemberID="viewController">
                     <layoutGuides>
                         <viewControllerLayoutGuide type="top" id="y3c-jy-aDJ"/>
                         <viewControllerLayoutGuide type="bottom" id="wfy-db-euE"/>