Move the notion of current Tab from TabModel to WebStateList.

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>
 
@@ skipping 20 matching lines @@
 
   explicit WebStateList(WebStateOwnership ownership = WebStateBorrowed);
   ~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.
+  int active_index() const { return active_index_; }
+
   // Returns true if the specified index is contained by the model.
   bool ContainsIndex(int index) const;
 
+  // Returns the currently active WebState or null if there is none.
+  web::WebState* GetActiveWebState() const;
+
   // Returns the WebState at the specified index. It is invalid to call this
   // with an index such that |ContainsIndex(index)| returns false.
   web::WebState* GetWebStateAt(int index) const;
 
   // Returns the index of the specified WebState or kInvalidIndex if the
   // WebState is not in the model.
   int GetIndexOfWebState(const web::WebState* web_state) const;
 
   // Returns the WebState that opened the WebState at the specified index or
   // null if there is no opener on record.
@@ skipping 38 matching lines @@
   // Replaces the WebState at the specified index with new WebState. Returns
   // the old WebState at that index to the caller (abandon ownership of the
   // returned WebState). An optional opener for the new WebState may be passed.
   web::WebState* ReplaceWebStateAt(int index,
                                    web::WebState* web_state,
                                    web::WebState* opener);
 
   // Detaches the WebState at the specified index.
   void DetachWebStateAt(int index);
 
+  // Makes the WebState at the specified index the active WebState.
+  void ActivateWebStateAt(int index);
+
   // 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:
   // Sets the opener of any WebState that reference the WebState at the
   // specified index to null.
   void FixOpenersReferencing(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;
   const WebStateOwnership web_state_ownership_;
   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_