Upstream Chrome on iOS source code [9/11].

ios/chrome/browser/ui/tab_switcher/session_changes.h

+// Copyright 2016 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_UI_TAB_SWITCHER_SESSION_CHANGES_H_
+#define IOS_CHROME_BROWSER_UI_TAB_SWITCHER_SESSION_CHANGES_H_
+
+#include <vector>
+
+namespace ios_internal {
+
+// This structure represents the changes a session undergoes.
+// It is used to update the UICollectionView showing a set of tabs.
+class SessionChanges {
+ public:
+  SessionChanges(std::vector<size_t> const& tabHashesInInitialState,
+                 std::vector<size_t> const& tabHashesInFinalState);
+  ~SessionChanges();
+  SessionChanges(const SessionChanges& sessionChanges) = delete;
+  SessionChanges& operator=(const SessionChanges& sessionChanges) = delete;
+
+  std::vector<size_t> const& deletions() const;
+  std::vector<size_t> const& insertions() const;
+  std::vector<size_t> const& updates() const;
+
+  bool hasChanges() const;
+
+ private:
+  // Those vectors contain indexes of tabs.
+  // The indexes are relative to a tab model snapshot, or a distant session.
+  // To be in accordance with the UICollectionView's |performBatchUpdates|
+  // method:
+  // -the indexes in |updates| are relative to the previous state of the
+  // session.
+  // -the indexes in |deletions| are relative to the previous state of the
+  // session.
+  // -the indexes in |insertions| are relative to the final state of the
+  // session.
+  std::vector<size_t> deletions_;
+  std::vector<size_t> insertions_;
+  std::vector<size_t> updates_;
+};
+
+}  // namespace ios_internal
+
+#endif  // IOS_CHROME_BROWSER_UI_TAB_SWITCHER_SESSION_CHANGES_H_