Added NavigationManager::GetIndexOfItem().

ios/chrome/browser/tabs/tab.mm

Index: ios/chrome/browser/tabs/tab.mm
diff --git a/ios/chrome/browser/tabs/tab.mm b/ios/chrome/browser/tabs/tab.mm
index 02a6e5223b3406acf0d20f905cd4cce04c3afacf..7584a08126494f875eb2c325c02351707ec82809 100644
--- a/ios/chrome/browser/tabs/tab.mm
+++ b/ios/chrome/browser/tabs/tab.mm
@@ -108,7 +108,6 @@
 #include "ios/public/provider/chrome/browser/chrome_browser_provider.h"
 #import "ios/public/provider/chrome/browser/native_app_launcher/native_app_metadata.h"
 #import "ios/public/provider/chrome/browser/native_app_launcher/native_app_whitelist_manager.h"
-#import "ios/web/navigation/crw_session_controller.h"
 #import "ios/web/navigation/navigation_item_impl.h"
 #import "ios/web/navigation/navigation_manager_impl.h"
 #include "ios/web/public/favicon_status.h"
@@ -1076,14 +1075,10 @@ - (BOOL)canGoForward {
 
 - (void)goToItem:(const web::NavigationItem*)item {
   DCHECK(item);
-
-  if (self.navigationManager) {
-    CRWSessionController* sessionController =
-        [self navigationManagerImpl]->GetSessionController();
-    NSInteger itemIndex = [sessionController indexOfItem:item];
-    DCHECK_NE(itemIndex, NSNotFound);
-    self.navigationManager->GoToIndex(itemIndex);
-  }
+  DCHECK(self.navigationManager);

[Eugene But (OOO till 7-30), 2017/06/02 18:08:08]

No need to DCHECK before dereferencing the pointer.

[kkhorimoto, 2017/06/02 18:28:58]

Done.

+  int index = self.navigationManager->GetIndexOfItem(item);
+  DCHECK_NE(index, NSNotFound);

[Eugene But (OOO till 7-30), 2017/06/02 18:08:08]

NSNotFound is NSInteger, so it will never be equal to int on 64-bit platform
(int there is 32-bit and NSInteger is 64-bit)

[kkhorimoto, 2017/06/02 18:28:58]

Done.

+  self.navigationManager->GoToIndex(index);
 }
 
 - (BOOL)openExternalURL:(const GURL&)url