fix(messaging, ios): register app delegate with google utilities for swizzling (#13525)

Author: russellwheatley

.gitignore

@@ -80,5 +80,4 @@ firebase-debug.log
 firestore-debug.log
 database-debug.log
 ui-debug.log
-
-**/.build/**/*
+**/.build/**/* 

packages/firebase_messaging/firebase_messaging/ios/Classes/FLTFirebaseMessagingPlugin.h

@@ -43,6 +43,7 @@ API_AVAILABLE(ios(10.0))
 @interface FLTFirebaseMessagingPlugin : FLTFirebasePlugin <FlutterPlugin,
                                                            FLTFirebasePlugin,
                                                            FIRMessagingDelegate,
+                                                           UIApplicationDelegate,
                                                            UNUserNotificationCenterDelegate>
 #else
 @interface FLTFirebaseMessagingPlugin

packages/firebase_messaging/firebase_messaging/ios/Classes/FLTFirebaseMessagingPlugin.m

@@ -225,9 +225,6 @@ - (void)application_onDidFinishLaunchingNotification:(nonnull NSNotification *)n
   _initialNotificationGathered = YES;
   [self initialNotificationCallback];
 
-#if TARGET_OS_OSX
-  // For macOS we use swizzling to intercept as addApplicationDelegate does not exist on the macOS
-  // registrar Flutter implementation.
   [GULAppDelegateSwizzler registerAppDelegateInterceptor:self];
   [GULAppDelegateSwizzler proxyOriginalDelegateIncludingAPNSMethods];
 
@@ -246,7 +243,11 @@ - (void)application_onDidFinishLaunchingNotification:(nonnull NSNotification *)n
                     didReceiveRemoteNotificationWithCompletionSEL,
                     method_getImplementation(donorMethod), method_getTypeEncoding(donorMethod));
   }
-#else
+#if !TARGET_OS_OSX
+  // `[_registrar addApplicationDelegate:self];` alone doesn't work for notifications to be received
+  // without the above swizzling This commit:
+  // https://github.com/google/GoogleUtilities/pull/162/files#diff-6bb6d1c46632fc66405a524071cc4baca5fc6a1a6c0eefef81d8c3e2c89cbc13L520-L533
+  // broke notifications which was released with firebase-ios-sdk v11.0.0
   [_registrar addApplicationDelegate:self];
 #endif