[Catalog] Fix Tabs example for rotation (#2019)

* [Catalog] Fix Tabs example for rotation

When the last tab was selected and the scroll view was all the way to
the right, rotating the device from portrait to landscape would cause
the scroll view to reposition itself. This resulted in half of each of
the two screens being visible.

* Marking size unused

* Fixing swift example. Unmarking "size" as unused

components/Tabs/examples/supplemental/TabBarIconExampleSupplemental.m

@@ -268,6 +268,16 @@ - (UIStatusBarStyle)preferredStatusBarStyle {
   return UIStatusBarStyleLightContent;
 }
 
+- (void)viewWillTransitionToSize:(CGSize)size
+       withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator {
+  [coordinator animateAlongsideTransition:
+      ^(__unused id<UIViewControllerTransitionCoordinatorContext>  _Nonnull context) {
+    // Update the scrollView position so that the selected view is entirely visible
+    [self tabBar:self.tabBar didSelectItem:self.tabBar.selectedItem];
+  } completion:nil];
+  [super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];
+}
+
 @end
 
 @implementation TabBarIconExample (CatalogByConvention)

components/Tabs/examples/supplemental/TabBarIconExampleSupplemental.swift

@@ -224,6 +224,15 @@ extension TabBarIconSwiftExample {
   override var childViewControllerForStatusBarStyle: UIViewController? {
     return appBar.headerViewController
   }
+
+  override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
+    coordinator.animate(alongsideTransition: { (_) in
+      if let selectedItem = self.tabBar.selectedItem {
+        self.tabBar(self.tabBar, didSelect: selectedItem)
+      }
+    }, completion: nil)
+    super.viewWillTransition(to: size, with: coordinator)
+  }
 }
 
 // MARK: - Catalog by convention