Introduce WebStateList to manage a list of web::WebState.

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/macros.h"
+#include "base/observer_list.h"
+
+class WebStateListObserver;
+
+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();
+
+  // Returns whether the model is empty or not.
+  bool empty() const { return web_state_wrappers_.empty(); }
+
+  // Returns the number of WebStates in the model.
+  size_t count() const { return web_state_wrappers_.size(); }
+
+  // Returns true if the specified index is contained by the model.
+  bool ContainsIndex(size_t index) const;
+
+  // Returns the WebState at the specified index. It is invalid to call this
+  // with an index such that |ContainsIndex(index)| returns fals.e

[marq (ping after 24h), 2017/02/13 16:32:53]

s/.e/e./, or f.xp in vi.

[sdefresne, 2017/02/14 13:39:56]

Done (note: that's Ctrl+t when the cursor is after the e in both emacs and
Xcode).

+  web::WebState* GetWebStateAt(size_t index) const;
+
+  // Returns the index of the specified WebState or kInvalidIndex if the
+  // WebState is not in the model.
+  size_t GetIndexOfWebState(const web::WebState* web_state) const;
+
+  // Inserts the specified WebState at the specified index.
+  void InsertWebState(size_t index, web::WebState* web_state);
+
+  // Moves the WebState at the specified index to another index.
+  void MoveWebStateAt(size_t from_index, size_t to_index);
+
+  // 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).
+  web::WebState* ReplaceWebStateAt(size_t index, web::WebState* web_state);
+
+  // Removes the WebState at the specified index.
+  void RemoveWebStateAt(size_t 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 size_t kInvalidIndex = static_cast<size_t>(-1);
+
+ private:
+  class WebStateWrapper;
+  const WebStateOwnership web_state_ownership_;
+  std::vector<std::unique_ptr<WebStateWrapper>> web_state_wrappers_;
+
+  // List of observers notified of changes to the model.
+  base::ObserverList<WebStateListObserver, true> observers_;
+
+  DISALLOW_COPY_AND_ASSIGN(WebStateList);
+};
+
+#endif  // IOS_SHARED_CHROME_BROWSER_TABS_WEB_STATE_LIST_H_