[ios] Add a delegate to WebStateList class.

ios/shared/chrome/browser/tabs/web_state_list.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_H_
 #define IOS_SHARED_CHROME_BROWSER_TABS_WEB_STATE_LIST_H_
 
 #include <memory>
 #include <vector>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/observer_list.h"
 #include "ui/base/page_transition_types.h"
 
+class WebStateListDelegate;
 class WebStateListObserver;
 class WebStateListOrderController;
 
 namespace web {
 class WebState;
 }
 
 // Manages a list of WebStates. May owns the WebState depending on the ownership
 // setting (initialised during construction, should eventually always be "owned"
 // once ownership of Tab is sane, see http://crbug.com/546222 for progress).
 class WebStateList {
  public:
   enum WebStateOwnership {
     WebStateBorrowed,
     WebStateOwned,
   };
 
-  explicit WebStateList(WebStateOwnership ownership = WebStateBorrowed);
+  WebStateList(WebStateListDelegate* delegate, WebStateOwnership ownership);
   ~WebStateList();
 
   // Returns whether the model is empty or not.
   bool empty() const { return web_state_wrappers_.empty(); }
 
   // Returns the number of WebStates in the model.
   int count() const { return static_cast<int>(web_state_wrappers_.size()); }
 
   // Returns the index of the currently active WebState, or kInvalidIndex if
   // there are no active WebState.
@@ skipping 70 matching lines @@
   // Adds an observer to the model.
   void AddObserver(WebStateListObserver* observer);
 
   // Removes an observer from the model.
   void RemoveObserver(WebStateListObserver* observer);
 
   // Invalid index.
   static const int kInvalidIndex = -1;
 
  private:
+  class WebStateWrapper;
+
   // Sets the opener of any WebState that reference the WebState at the
   // specified index to null.
   void ClearOpenersReferencing(int index);
 
   // Notify the observers if the active WebState change.
   void NotifyIfActiveWebStateChanged(web::WebState* old_web_state,
                                      bool user_action);
 
   // Returns the index of the |n|-th WebState (with n > 0) in the sequence of
   // WebStates opened from the specified WebState after |start_index|, or
   // kInvalidIndex if there are no such WebState. If |use_group| is true, the
   // opener's navigation index is used to detect navigation changes within the
   // same session.
   int GetIndexOfNthWebStateOpenedBy(const web::WebState* opener,
                                     int start_index,
                                     bool use_group,
                                     int n) const;
 
-  class WebStateWrapper;
+  // The WebStateList delegate.
+  WebStateListDelegate* delegate_;
+
+  // Whether this WebStateList owns the WebState it hosts.
+  // TODO(crbug.com/546222): remove once this is always "owned".
   const WebStateOwnership web_state_ownership_;
+
+  // Wrappers to the WebStates hosted by the WebStateList.
   std::vector<std::unique_ptr<WebStateWrapper>> web_state_wrappers_;
 
   // An object that determines where new WebState should be inserted and where
   // selection should move when a WebState is detached.
   std::unique_ptr<WebStateListOrderController> order_controller_;
 
   // List of observers notified of changes to the model.
   base::ObserverList<WebStateListObserver, true> observers_;
 
   // Index of the currently active WebState, kInvalidIndex if no such WebState.
   int active_index_ = kInvalidIndex;
 
   DISALLOW_COPY_AND_ASSIGN(WebStateList);
 };
 
 #endif  // IOS_SHARED_CHROME_BROWSER_TABS_WEB_STATE_LIST_H_