Change deprecated keyWindow to new API

Author: themiswang

FirebasePerformance/Sources/Instrumentation/UIKit/FPRUIViewControllerInstrument.m

@@ -14,6 +14,7 @@
 
 #import <TargetConditionals.h>
 #import <UIKit/UIKit.h>
+#import <UIKit/UIWindowScene.h>
 
 #import "FirebasePerformance/Sources/AppActivity/FPRScreenTraceTracker+Private.h"
 #import "FirebasePerformance/Sources/Common/FPRDiagnostics.h"
@@ -69,12 +70,22 @@ void InstrumentViewDidAppear(FPRUIViewControllerInstrument *instrument,
 
     // This has to be called on the main thread and so it's done here instead of in
     // FPRScreenTraceTracker.
-    // TODO(#13067): Replace keyWindow usage (deprecated in iOS and unavailable in visionOS).
 #if !defined(TARGET_OS_VISION) || !TARGET_OS_VISION
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wdeprecated-declarations"
-    if ([((UIViewController *)_self).view isDescendantOfView:FPRSharedApplication().keyWindow]) {
-#pragma clang diagnostic pop
+    NSArray *windows;
+    if (@available(iOS 13.0, *)) {
+      NSArray *scenes = FPRSharedApplication().connectedScenes.allObjects;
+      windows = [[scenes objectAtIndex:0] windows];
+    } else {
+      windows = FPRSharedApplication().windows;
+    }
+    UIWindow *foundKeyWindow;
+    for (UIWindow *window in windows) {
+      if (window.isKeyWindow) {
+        foundKeyWindow = window;
+        break;
+      }
+    }
+    if (foundKeyWindow && [((UIViewController *)_self).view isDescendantOfView:foundKeyWindow]) {
       [[FPRScreenTraceTracker sharedInstance] viewControllerDidAppear:_self];
     }
 #endif