Add WebStateListOrderController to control WebState insertion.

ios/chrome/browser/tabs/tab_model_order_controller.mm

 // Copyright 2012 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/chrome/browser/tabs/tab_model_order_controller.h"
 
 #include "base/logging.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 @implementation TabModelOrderController {
   __weak TabModel* model_;
 }
 
 - (instancetype)initWithTabModel:(TabModel*)model {
   DCHECK(model);
   if ((self = [super init]))
     model_ = model;
   return self;
 }
 
-- (NSUInteger)insertionIndexForTab:(Tab*)newTab
-                        transition:(ui::PageTransition)transition
-                            opener:(Tab*)parentTab
-                         adjacency:(TabModelOrderConstants::InsertionAdjacency)
-                                       adjacency {
-  if (model_.isEmpty)
-    return 0;
-
-  if (!parentTab)
-    return [self insertionIndexForAppending];
-
-  if (!PageTransitionCoreTypeIs(transition, ui::PAGE_TRANSITION_LINK))
-    return [self insertionIndexForAppending];
-
-  NSUInteger referenceIndex = [model_ indexOfTab:parentTab];
-  Tab* openLocation = [model_ lastTabWithOpener:parentTab];
-  if (openLocation)
-    referenceIndex = [model_ indexOfTab:openLocation];
-
-  DCHECK_NE(referenceIndex, static_cast<NSUInteger>(NSNotFound));
-  return referenceIndex + 1;
-}
-
-- (NSUInteger)insertionIndexForAppending {
-  return model_.count;
-}
-
 - (Tab*)determineNewSelectedTabFromRemovedTab:(Tab*)removedTab {
   // While the desktop version of this code deals in indices, this deals in
   // actual tabs. As a result, the tab only needs to change iff the selection
   // is the tab that's removed.
   if (removedTab != model_.currentTab)
     return model_.currentTab;
 
   const NSUInteger numberOfTabs = model_.count;
   if (numberOfTabs < 2)
     return nil;
@@ skipping 24 matching lines @@
   NSUInteger selectedIndex = [model_ indexOfTab:removedTab];
   DCHECK(selectedIndex <= numberOfTabs - 1);
   // Is the closing tab the last one? If so, return the penultimate tab.
   if (selectedIndex == numberOfTabs - 1)
     return [model_ tabAtIndex:selectedIndex - 1];
   // Otherwise return the next tab after the current tab.
   return [model_ tabAtIndex:selectedIndex + 1];
 }
 
 @end