Moved serialization out of CRWSessionEntry.

ios/web/navigation/navigation_item_storage_builder.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_WEB_NAVIGATION_NAVIGATION_ITEM_STORAGE_BUILDER_H_
+#define IOS_WEB_NAVIGATION_NAVIGATION_ITEM_STORAGE_BUILDER_H_
+
+#include <memory>
+
+@class CRWNavigationItemStorage;
+
+namespace web {
+
+class NavigationItemImpl;
+
+// Class that can serialize and deserialize NavigationItems.
+class NavigationItemStorageBuilder {
+ public:
+  // Creates a serialized NavigationItem from |navigation_Item|.
+  CRWNavigationItemStorage* BuildSerialization(
+      NavigationItemImpl* navigation_item) const;
+  // Creates a NavigationItem from |navigation_Item_storage|.
+  std::unique_ptr<NavigationItemImpl> BuildNavigationItemImpl(
+      CRWNavigationItemStorage* navigation_item_storage) const;
+};
+
+}  // namespace web
+
+#endif  // IOS_WEB_NAVIGATION_NAVIGATION_ITEM_STORAGE_BUILDER_H_