Coordinators are now notified when moving to a parent coordinator.

ios/clean/chrome/browser/browser_coordinator.mm

Index: ios/clean/chrome/browser/browser_coordinator.mm
diff --git a/ios/clean/chrome/browser/browser_coordinator.mm b/ios/clean/chrome/browser/browser_coordinator.mm
index f3f79a7fb4e0dd747eff5eb5dfe0411f609f4413..4c3b0ecce2c22c8ee33c6f5ebe241fbf11e46394 100644
--- a/ios/clean/chrome/browser/browser_coordinator.mm
+++ b/ios/clean/chrome/browser/browser_coordinator.mm
@@ -72,6 +72,7 @@
   coordinator.parentCoordinator = self;
   coordinator.browser = self.browser;
   coordinator.context.baseViewController = self.viewController;
+  [coordinator coordinatorDidMoveToParentCoordinator:self];
 }
 
 - (BrowserCoordinator*)overlayCoordinator {
@@ -126,6 +127,11 @@
   coordinator.parentCoordinator = nil;
 }
 
+- (void)coordinatorDidMoveToParentCoordinator:
+    (BrowserCoordinator*)parentCoordinator {
+  // Default implementation is a no-op.
+}
+
 - (void)childCoordinatorDidStart:(BrowserCoordinator*)childCoordinator {
   // Default implementation is a no-op.
 }