Added web::GetCommittedItemWithUniqueID function.

ios/web/navigation/navigation_manager_util.h

Index: ios/web/navigation/navigation_manager_util.h
diff --git a/ios/web/navigation/navigation_manager_util.h b/ios/web/navigation/navigation_manager_util.h
new file mode 100644
index 0000000000000000000000000000000000000000..0c22977528f5381d3eb34d19d105173155c77c31
--- /dev/null
+++ b/ios/web/navigation/navigation_manager_util.h
@@ -0,0 +1,31 @@
+// 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_MANAGER_UTIL_H_
+#define IOS_WEB_NAVIGATION_NAVIGATION_MANAGER_UTIL_H_
+
+// This file contains extensions for web::NavigationManager API without making
+// them part of ios/web/public.
+
+namespace web {
+
+class NavigationItem;
+class NavigationManager;
+
+// Returns committed navigation item with given |unique_id| or null if item
+// is not found or it is pending or transient. Item's unique id is retrieved
+// via GetUniqueID method.
+NavigationItem* GetCommittedItemWithUniqueID(
+    NavigationManager* navigation_manager,
+    int unique_id);
+
+// Returns committed navigation item index with given |unique_id| or -1 if item
+// is not found or it is pending or transient. Item's unique id is retrieved
+// via GetUniqueID method.
+int GetCommittedItemIndexWithUniqueID(NavigationManager* navigation_manager,
+                                      int unique_id);
+
+}  // namespace web
+
+#endif  // IOS_WEB_NAVIGATION_NAVIGATION_MANAGER_UTIL_H_