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

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

Index: ios/shared/chrome/browser/tabs/web_state_list.h
diff --git a/ios/shared/chrome/browser/tabs/web_state_list.h b/ios/shared/chrome/browser/tabs/web_state_list.h
new file mode 100644
index 0000000000000000000000000000000000000000..5964e01069e1a13b13939370495e6a624eaa765a
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+++ b/ios/shared/chrome/browser/tabs/web_state_list.h
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+// 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.
+  int count() const { return static_cast<int>(web_state_wrappers_.size()); }
+
+  // Returns true if the specified index is contained by the model.
+  bool ContainsIndex(int index) 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;
+
+  // Inserts the specified WebState at the specified index.
+  void InsertWebState(int index, web::WebState* web_state);
+
+  // Moves the WebState at the specified index to another index.
+  void MoveWebStateAt(int from_index, int 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(int index, web::WebState* web_state);
+
+  // Detaches the WebState at the specified index.
+  void DetachWebStateAt(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:
+  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_