Revert of [ios] Move WebStateList to ios/chrome/browser/web_state_list.

ios/chrome/browser/web_state_list/web_state_list_observer.h

Index: ios/chrome/browser/web_state_list/web_state_list_observer.h
diff --git a/ios/chrome/browser/web_state_list/web_state_list_observer.h b/ios/chrome/browser/web_state_list/web_state_list_observer.h
deleted file mode 100644
index 7cc887acccd2e4009b224314898daafe2b148eb0..0000000000000000000000000000000000000000
--- a/ios/chrome/browser/web_state_list/web_state_list_observer.h
+++ /dev/null
@@ -1,74 +0,0 @@
-// 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_CHROME_BROWSER_WEB_STATE_LIST_WEB_STATE_LIST_OBSERVER_H_
-#define IOS_CHROME_BROWSER_WEB_STATE_LIST_WEB_STATE_LIST_OBSERVER_H_
-
-#include "base/macros.h"
-
-class WebStateList;
-
-namespace web {
-class WebState;
-}
-
-// Interface for listening to events occurring to WebStateLists.
-class WebStateListObserver {
- public:
-  WebStateListObserver();
-  virtual ~WebStateListObserver();
-
-  // Invoked after a new WebState has been added to the WebStateList at the
-  // specified index.
-  virtual void WebStateInsertedAt(WebStateList* web_state_list,
-                                  web::WebState* web_state,
-                                  int index);
-
-  // Invoked after the WebState at the specified index is moved to another
-  // index.
-  virtual void WebStateMoved(WebStateList* web_state_list,
-                             web::WebState* web_state,
-                             int from_index,
-                             int to_index);
-
-  // Invoked after the WebState at the specified index is replaced by another
-  // WebState.
-  virtual void WebStateReplacedAt(WebStateList* web_state_list,
-                                  web::WebState* old_web_state,
-                                  web::WebState* new_web_state,
-                                  int index);
-
-  // Invoked before the specified WebState is detached from the WebStateList.
-  // The WebState is still valid and still in the WebStateList.
-  virtual void WillDetachWebStateAt(WebStateList* web_state_list,
-                                    web::WebState* web_state,
-                                    int index);
-
-  // Invoked after the WebState at the specified index has been detached. The
-  // WebState is still valid but is no longer in the WebStateList.
-  virtual void WebStateDetachedAt(WebStateList* web_state_list,
-                                  web::WebState* web_state,
-                                  int index);
-
-  // Invoked before the specified WebState is destroyed via the WebStateList.
-  // The WebState is still valid but is no longer in the WebStateList.
-  virtual void WillCloseWebStateAt(WebStateList* web_state_list,
-                                   web::WebState* web_state,
-                                   int index);
-
-  // Invoked after |new_web_state| 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, |user_action| will
-  // be true.
-  virtual void WebStateActivatedAt(WebStateList* web_state_list,
-                                   web::WebState* old_web_state,
-                                   web::WebState* new_web_state,
-                                   int active_index,
-                                   bool user_action);
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(WebStateListObserver);
-};
-
-#endif  // IOS_CHROME_BROWSER_WEB_STATE_LIST_WEB_STATE_LIST_OBSERVER_H_