Remove obsolete code in TabModelOrderController.

ios/chrome/browser/tabs/tab_model.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.h"
 
 #include <utility>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 346 matching lines @@
     Tab* current = [_tabs objectAtIndex:i];
     DCHECK([current navigationManager]);
     CRWSessionController* sessionController =
         [current navigationManager]->GetSessionController();
     if ([sessionController.openerId isEqualToString:parentID])
       return current;
   }
   return nil;
 }
 
-- (Tab*)firstTabWithOpener:(Tab*)tab {
-  if (!tab)
-    return nil;
-  NSUInteger stopIndex = [self indexOfTab:tab];
-  if (stopIndex == NSNotFound)
-    return nil;
-  NSString* parentID = tab.tabId;
-  // Match the navigation index as well as the session id, to better match the
-  // state of the tab. I.e. two tabs are opened via a link from tab A, and then
-  // a new url is loaded into tab A, and more tabs opened from that url, the
-  // latter two tabs should not be grouped with the former two. The navigation
-  // index is the simplest way to detect navigation changes.
-  DCHECK([tab navigationManager]);
-  NSInteger parentNavIndex = [tab navigationManager]->GetCurrentItemIndex();
-  for (NSUInteger i = 0; i < stopIndex; ++i) {
-    Tab* tabToCheck = [_tabs objectAtIndex:i];
-    DCHECK([tabToCheck navigationManager]);
-    CRWSessionController* sessionController =
-        [tabToCheck navigationManager]->GetSessionController();
-    if ([sessionController.openerId isEqualToString:parentID] &&
-        sessionController.openerNavigationIndex == parentNavIndex) {
-      return tabToCheck;
-    }
-  }
-  return nil;
-}
-
 - (Tab*)lastTabWithOpener:(Tab*)tab {
   NSUInteger startIndex = [self indexOfTab:tab];
   if (startIndex == NSNotFound)
     return nil;
   // There is at least one tab in the model, because otherwise the above check
   // would have returned.
   NSString* parentID = tab.tabId;
   DCHECK([tab navigationManager]);
   NSInteger parentNavIndex = [tab navigationManager]->GetCurrentItemIndex();
 
@@ skipping 667 matching lines @@
   web::NavigationManager::WebLoadParams params(URL);
   params.referrer = referrer;
   params.transition_type = ui::PAGE_TRANSITION_TYPED;
   [[tab webController] loadWithParams:params];
   [tab webController].webUsageEnabled = webUsageEnabled_;
   [self insertTab:tab atIndex:index];
   return tab;
 }
 
 @end