Call |NavigationItemsPruned| when item is removed in session controller.

ios/web/navigation/crw_session_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/web/navigation/crw_session_controller.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <utility>
@@ skipping 530 matching lines @@
   DCHECK(index != _lastCommittedItemIndex);
   DCHECK(index >= 0);
 
   [self discardNonCommittedItems];
 
   _items.erase(_items.begin() + index);
   if (_lastCommittedItemIndex > index)
     _lastCommittedItemIndex--;
   if (_previousItemIndex >= index)
     _previousItemIndex--;
+
+  if (_navigationManager)
+    _navigationManager->OnNavigationItemsPruned(1U);
 }
 
 - (BOOL)isSameDocumentNavigationBetweenItem:(web::NavigationItem*)firstItem
                                     andItem:(web::NavigationItem*)secondItem {
   if (!firstItem || !secondItem || firstItem == secondItem)
     return NO;
   NSUInteger firstIndex = [self indexOfItem:firstItem];
   NSUInteger secondIndex = [self indexOfItem:secondItem];
   if (firstIndex == NSNotFound || secondIndex == NSNotFound)
     return NO;
@@ skipping 64 matching lines @@
   return item;
 }
 
 - (BOOL)isRedirectTransitionForItemAtIndex:(size_t)index {
   DCHECK_LT(index, self.items.size());
   ui::PageTransition transition = self.items[index]->GetTransitionType();
   return (transition & ui::PAGE_TRANSITION_IS_REDIRECT_MASK) ? YES : NO;
 }
 
 @end