[iOS] Adding a call back to the view controller when being popped

Adding a call back to the view controller when being popped.

Change-Id: Ib2b3800b3204ae52fd437681b4362a25682d15ec
Reviewed-on: https://chromium-review.googlesource.com/c/1425608
Commit-Queue: Jérôme Lebel <jlebel@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625250}

ios/chrome/browser/ui/settings/settings_navigation_controller.h

@@ -24,6 +24,10 @@ class ChromeBrowserState;
 // Notifies the controller that the settings screen is being dismissed.
 - (void)settingsWillBeDismissed;
 
+// Notifies the controller that is popped out from the settings navigation
+// controller.
+- (void)viewControllerWasPopped;
+
 @end
 
 @protocol SettingsNavigationControllerDelegate<NSObject>

ios/chrome/browser/ui/settings/settings_navigation_controller.mm

@@ -295,6 +295,16 @@ initWithRootViewController:(UIViewController*)rootViewController
   }
 }
 
+- (UIViewController*)popViewControllerAnimated:(BOOL)animated {
+  UIViewController* poppedViewController =
+      [super popViewControllerAnimated:animated];
+  if ([poppedViewController
+          respondsToSelector:@selector(viewControllerWasPopped)]) {
+    [poppedViewController performSelector:@selector(viewControllerWasPopped)];
+  }
+  return poppedViewController;
+}
+
 #pragma mark - Private
 
 // Creates an autoreleased "X" button that closes the settings when tapped.