Field trial removing tiles from NTP if URL is already open - for 1993 clients

chrome/browser/ui/tabs/tab_strip_model_utils.h

 // Copyright (c) 2012 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 CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_UTILS_H_
 #define CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_UTILS_H_
 
+#include <set>
+#include <string>
+
 class TabStripModel;
 
+namespace history {
+class TopSites;
+}
+
 namespace chrome {
 
 // Returns the index of the first tab that is blocked. This returns
 // |model->count()| if no tab is blocked.
 int IndexOfFirstBlockedTab(const TabStripModel* model);
 
+// Creates a set containing the canonical URLs of the currently open tabs.
+void GetOpenUrls(const TabStripModel& tabs,
+                 const history::TopSites& top_sites,
+                 std::set<std::string>* urls);
+
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_UTILS_H_