[iOS Clean] Removed old overlay implementation.

ios/clean/chrome/browser/ui/tab/tab_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.
 
 #import "ios/clean/chrome/browser/ui/tab/tab_coordinator.h"
 
 #include <memory>
 
 #include "base/mac/foundation_util.h"
 #include "base/memory/ptr_util.h"
@@ skipping 116 matching lines @@
 
 - (void)childCoordinatorWillStop:(BrowserCoordinator*)childCoordinator {
   if ([childCoordinator isKindOfClass:[FindInPageCoordinator class]]) {
     self.viewController.findBarViewController = nil;
   } else if ([childCoordinator isKindOfClass:[WebCoordinator class]] ||
              [childCoordinator isKindOfClass:[NTPCoordinator class]]) {
     self.viewController.contentViewController = nil;
   }
 }
 
-- (BOOL)canAddOverlayCoordinator:(BrowserCoordinator*)overlayCoordinator {
-  // This coordinator will always accept overlay coordinators.
-  return YES;
-}
-
 #pragma mark - Experiment support
 
 - (BOOL)usesBottomToolbar {
   NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
   NSString* bottomToolbarPreference =
       [defaults stringForKey:@"EnableBottomToolbar"];
   return [bottomToolbarPreference isEqualToString:@"Enabled"];
 }
 
 // Creates and returns a new view controller for use as a tab container;
@@ skipping 58 matching lines @@
   self.webState->GetNavigationManager()->LoadURLWithParams(params);
 }
 
 #pragma mark - TabStripCommands
 
 - (void)showTabStrip {
   self.viewController.tabStripVisible = YES;
 }
 
 @end