Handle iOS Universal Links

Author: AlBlanc

shell/platform/darwin/ios/framework/Source/FlutterAppDelegate.mm

@@ -227,9 +227,43 @@ - (BOOL)application:(UIApplication*)application
     continueUserActivity:(NSUserActivity*)userActivity
       restorationHandler:(void (^)(NSArray* __nullable restorableObjects))restorationHandler {
 #endif
-  return [_lifeCycleDelegate application:application
-                    continueUserActivity:userActivity
-                      restorationHandler:restorationHandler];
+          if ([_lifeCycleDelegate application:application
+                         continueUserActivity:userActivity
+                           restorationHandler:restorationHandler]) {
+            return YES;
+          }
+          else if (userActivity.activityType == NSUserActivityTypeBrowsingWeb) {
+              return NO;
+          } else {
+              NSURLComponents* components = [NSURLComponents componentsWithURL:userActivity.webpageURL resolvingAgainstBaseURL:YES];
+
+              if (components == nil or components.path == nil){
+                  return NO;
+              }
+              FlutterViewController* flutterViewController = [self rootFlutterViewController];
+              if (flutterViewController) {
+                  [flutterViewController.engine
+                   waitForFirstFrame:3.0
+                   callback:^(BOOL didTimeout) {
+                      if (didTimeout) {
+                          FML_LOG(ERROR)
+                          << "Timeout waiting for the first frame when launching a universal link.";
+                      } else {
+                          NSString* pathAndQuery = components.path;
+                          if (components.query != nil and [components.query length] != 0) {
+                              pathAndQuery =
+                              [NSString stringWithFormat:@"%@?%@", pathAndQuery, components.query];
+                          }
+                          [flutterViewController.engine.navigationChannel invokeMethod:@"pushRoute"
+                                                                             arguments:pathAndQuery];
+                      }
+                  }];
+                  return YES;
+              } else {
+                  FML_LOG(ERROR) << "Attempting to open a universal link without a Flutter RootViewController.";
+                  return NO;
+              }
+          }
 }
 
 #pragma mark - FlutterPluginRegistry methods. All delegating to the rootViewController