Coordinators are now notified when moving to a parent coordinator.

ios/clean/chrome/browser/browser_coordinator.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // ======                        New Architecture                         =====
 // =         This code is only used in the new iOS Chrome architecture.       =
 // ============================================================================
 
 #import "base/logging.h"
 #import "ios/clean/chrome/browser/browser_coordinator+internal.h"
@@ skipping 54 matching lines @@
 }
 
 - (void)addChildCoordinator:(BrowserCoordinator*)coordinator {
   CHECK([self respondsToSelector:@selector(viewController)])
       << "BrowserCoordinator implementations must provide a viewController "
          "property.";
   [self.childCoordinators addObject:coordinator];
   coordinator.parentCoordinator = self;
   coordinator.browser = self.browser;
   coordinator.context.baseViewController = self.viewController;
+  [coordinator coordinatorDidMoveToParentCoordinator:self];
 }
 
 - (BrowserCoordinator*)overlayCoordinator {
   if (self.overlaying)
     return self;
   for (BrowserCoordinator* child in self.children) {
     BrowserCoordinator* overlay = child.overlayCoordinator;
     if (overlay)
       return overlay;
   }
@@ skipping 34 matching lines @@
          self.childCoordinators.count == 0;
 }
 
 - (void)removeChildCoordinator:(BrowserCoordinator*)coordinator {
   if (![self.childCoordinators containsObject:coordinator])
     return;
   [self.childCoordinators removeObject:coordinator];
   coordinator.parentCoordinator = nil;
 }
 
+- (void)coordinatorDidMoveToParentCoordinator:
+    (BrowserCoordinator*)parentCoordinator {
+  // Default implementation is a no-op.
+}
+
 - (void)childCoordinatorDidStart:(BrowserCoordinator*)childCoordinator {
   // Default implementation is a no-op.
 }
 
 - (void)childCoordinatorWillStop:(BrowserCoordinator*)childCoordinator {
   // Default implementation is a no-op.
 }
 
 @end