[ios] Extend WebStateListObserver amd WebStateListDelegate APIs.

ios/shared/chrome/browser/tabs/web_state_list_observer_bridge.h

 // Copyright 2017 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.
 
 #ifndef IOS_SHARED_CHROME_BROWSER_TABS_WEB_STATE_LIST_OBSERVER_BRIDGE_H_
 #define IOS_SHARED_CHROME_BROWSER_TABS_WEB_STATE_LIST_OBSERVER_BRIDGE_H_
 
 #import <Foundation/Foundation.h>
 
 #include "base/macros.h"
@@ skipping 15 matching lines @@
 - (void)webStateList:(WebStateList*)webStateList
      didMoveWebState:(web::WebState*)webState
            fromIndex:(int)fromIndex
              toIndex:(int)toIndex;
 
 // Invoked after the WebState at the specified index is replaced by another
 // WebState.
 - (void)webStateList:(WebStateList*)webStateList
     didReplaceWebState:(web::WebState*)oldWebState
           withWebState:(web::WebState*)newWebState
-               atIndex:(int)index;
+               atIndex:(int)atIndex;
+
+// Invoked before the specified WebState is detached from the WebStateList.
+// The WebState is still valid and still in the WebStateList.
+- (void)webStateList:(WebStateList*)webStateList
+    willDetachWebState:(web::WebState*)webState
+               atIndex:(int)atIndex;
 
 // Invoked after the WebState at the specified index has been detached. The
 // WebState is still valid but is no longer in the WebStateList.
 - (void)webStateList:(WebStateList*)webStateList
     didDetachWebState:(web::WebState*)webState
-              atIndex:(int)index;
+              atIndex:(int)atIndex;
+
+// Invoked before the specified WebState is destroyed via the WebStateList.
+// The WebState is still valid but is no longer in the WebStateList.
+- (void)webStateList:(WebStateList*)webStateList
+    willCloseWebState:(web::WebState*)webState
+              atIndex:(int)atIndex;
 
 // Invoked after |newWebState| was activated at the specified index. Both
 // WebState are either valid or null (if there was no selection or there is
 // no selection). If the change is due to an user action, |userAction| will
 // be true.
 - (void)webStateList:(WebStateList*)webStateList
     didChangeActiveWebState:(web::WebState*)newWebState
                 oldWebState:(web::WebState*)oldWebState
                     atIndex:(int)atIndex
                  userAction:(BOOL)userAction;
@@ skipping 13 matching lines @@
                           web::WebState* web_state,
                           int index) override;
   void WebStateMoved(WebStateList* web_state_list,
                      web::WebState* web_state,
                      int from_index,
                      int to_index) override;
   void WebStateReplacedAt(WebStateList* web_state_list,
                           web::WebState* old_web_state,
                           web::WebState* new_web_state,
                           int index) override;
+  void WillDetachWebStateAt(WebStateList* web_state_list,
+                            web::WebState* web_state,
+                            int index) override;
   void WebStateDetachedAt(WebStateList* web_state_list,
                           web::WebState* web_state,
                           int index) override;
+  void WillCloseWebStateAt(WebStateList* web_state_list,
+                           web::WebState* web_state,
+                           int index) override;
   void WebStateActivatedAt(WebStateList* web_state_list,
                            web::WebState* old_web_state,
                            web::WebState* new_web_state,
                            int active_index,
                            bool user_action) override;
 
   id<WebStateListObserving> observer_;
 
   DISALLOW_COPY_AND_ASSIGN(WebStateListObserverBridge);
 };
 
 #endif  // IOS_SHARED_CHROME_BROWSER_TABS_WEB_STATE_LIST_OBSERVER_BRIDGE_H_