fix: duplicate fullscreen macOS menu item (#49597)

Co-authored-by: trop[bot] <37223003+trop[bot]@users.noreply.github.com>
Co-authored-by: Shelley Vohr <shelley.vohr@gmail.com>

shell/browser/mac/electron_application_delegate.mm

@@ -56,11 +56,6 @@ static NSDictionary* UNNotificationResponseToNSDictionary(
 }
 
 - (void)applicationWillFinishLaunching:(NSNotification*)notify {
-  // Don't add the "Enter Full Screen" menu item automatically.
-  [[NSUserDefaults standardUserDefaults]
-      setBool:NO
-       forKey:@"NSFullScreenMenuItemEverywhere"];
-
   [[[NSWorkspace sharedWorkspace] notificationCenter]
       addObserver:self
          selector:@selector(willPowerOff:)

shell/browser/ui/cocoa/electron_menu_controller.mm

@@ -560,6 +560,14 @@ NSArray* ConvertSharingItemToNS(const SharingItem& item) {
 
 - (void)menuWillOpen:(NSMenu*)menu {
   isMenuOpen_ = YES;
+
+  // macOS automatically injects a duplicate "Toggle Full Screen" menu item
+  // when we set menu.delegate on submenus. Remove hidden duplicates.
+  for (NSMenuItem* item in menu.itemArray) {
+    if (item.isHidden && item.action == @selector(toggleFullScreenMode:))
+      [menu removeItem:item];
+  }
+
   [self refreshMenuTree:menu];
   if (model_)
     model_->MenuWillShow();