Remove code in subclasses already performed by the base class.

ios/clean/chrome/browser/ui/root/root_coordinator.mm

 // Copyright 2017 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.
 
 #import "ios/clean/chrome/browser/ui/root/root_coordinator.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
@@ skipping 21 matching lines @@
   self.viewController = [[RootContainerViewController alloc] init];
 
   TabGridCoordinator* tabGridCoordinator = [[TabGridCoordinator alloc] init];
   [self addChildCoordinator:tabGridCoordinator];
   [tabGridCoordinator start];
   self.tabGridCoordinator = tabGridCoordinator;
 
   [super start];
 }
 
 - (void)stop {

[marq (ping after 24h), 2017/04/18 12:13:26]

can this whole method go away now?

[lpromero, 2017/05/03 13:13:23]

No, to balance in stop the child coordinators additions from start. The parent
class only removes all child coordinators in dealloc.

   [super stop];
-  // PLACEHOLDER: Stop child coordinators here for now. We might deal with this
+  // PLACEHOLDER: Remove child coordinators here for now. This might be handled
   // differently later on.
   for (BrowserCoordinator* child in self.children) {
-    [child stop];
     [self removeChildCoordinator:child];
   }
 }
 
 - (void)childCoordinatorDidStart:(BrowserCoordinator*)childCoordinator {
   self.viewController.contentViewController = childCoordinator.viewController;
 }
 
 - (void)childCoordinatorWillStop:(BrowserCoordinator*)childCoordinator {
   self.viewController.contentViewController = nil;
 }
 
 - (BOOL)canAddOverlayCoordinator:(BrowserCoordinator*)overlayCoordinator {
   return YES;
 }
 
 #pragma mark - URLOpening
 
 - (void)openURL:(NSURL*)URL {
   [self.tabGridCoordinator openURL:URL];
 }
 
 @end