BrowserCoordinator stops its children.

ios/clean/chrome/browser/ui/ntp/ntp_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/ntp/ntp_coordinator.h"
 
 #include "base/logging.h"
 #include "ios/chrome/browser/ui/ui_util.h"
 #import "ios/clean/chrome/browser/ui/bookmarks/bookmarks_coordinator.h"
 #import "ios/clean/chrome/browser/ui/commands/ntp_commands.h"
@@ skipping 29 matching lines @@
   [dispatcher startDispatchingToTarget:self
                            forSelector:@selector(showNTPBookmarksPanel)];
   [dispatcher startDispatchingToTarget:self
                            forSelector:@selector(showNTPRecentTabsPanel)];
   self.viewController.dispatcher = static_cast<id>(self.browser->dispatcher());
   [super start];
 }
 
 - (void)stop {
   [super stop];
-  // PLACEHOLDER: Stop child coordinators here for now. We might deal with this
-  // differently later on.
-  for (BrowserCoordinator* child in self.children) {
-    [child stop];
-  }
   [self.browser->dispatcher() stopDispatchingToTarget:self];
 }
 
 - (void)childCoordinatorDidStart:(BrowserCoordinator*)coordinator {
   if ([coordinator isKindOfClass:[NTPHomeCoordinator class]]) {
     self.viewController.homeViewController = coordinator.viewController;
 
   } else if ([coordinator isKindOfClass:[BookmarksCoordinator class]]) {
     if (IsIPadIdiom()) {
       self.viewController.bookmarksViewController = coordinator.viewController;
@@ skipping 29 matching lines @@
 }
 
 - (void)showNTPRecentTabsPanel {
   RecentTabsCoordinator* panelCoordinator =
       [[RecentTabsCoordinator alloc] init];
   [self addChildCoordinator:panelCoordinator];
   [panelCoordinator start];
 }
 
 @end