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

chrome/browser/history/most_visited_tiles_experiment.h

Index: chrome/browser/history/most_visited_tiles_experiment.h
diff --git a/chrome/browser/history/most_visited_tiles_experiment.h b/chrome/browser/history/most_visited_tiles_experiment.h
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+// Copyright (c) 2013 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_HISTORY_MOST_VISITED_TILES_EXPERIMENT_H_
+#define CHROME_BROWSER_HISTORY_MOST_VISITED_TILES_EXPERIMENT_H_
+
+#include "base/values.h"
+#include "chrome/browser/history/history_types.h"
+#include "chrome/common/instant_types.h"
+
+class ListValue;
+class InstantMostVisitedItem;
+
+namespace history {
+
+// This enum is also defined in histograms.xml. These values represent the
+// types of actions carried out by the Most Visited Tile Placement experiment.
+enum NtpTileExperimentActions {
+  NTP_TILE_EXPERIMENT_ACTION_REMOVED_URL = 0,
+  NTP_TILE_EXPERIMENT_ACTION_DID_NOT_REMOVE_URL = 1,
+  NTP_TILE_EXPERIMENT_ACTION_TOO_FEW_URLS_TILES_1_8 = 2,
+  NTP_TILE_EXPERIMENT_ACTION_TOO_FEW_URLS_TILES_1_4 = 3,
+  // The number of Most Visited Tile Placement experiment actions logged.
+  NUM_NTP_TILE_EXPERIMENT_ACTIONS
+};
+
+// Class for implementing the Most Visited Tile Placement experiment.
+class MostVisitedTilesExperiment {
+ public:
+  // Helper method to shuffle MostVisited tiles for A/B testing purposes.
+  static void MaybeShuffle(MostVisitedURLList* data);
+
+  // Returns true if this user is part of the Most Visited Tile Placement
+  // experiment group where URLs currently open in another browser tab are not
+  // displayed on an NTP tile. Note: the experiment targets only the top-level
+  // of sites i.e. if www.foo.com/bar is open in browser, and www.foo.com is a
+  // recommended URL, www.foo.com will still appear on the next NTP open. The
+  // experiment will not remove a URL if doing so would cause the number of Most
+  // Visited recommendations to drop below eight.
+  static bool IsDontShowOpenURLsEnabled();
+
+  // Removes URLs already open in browser, for 1993 clients, if part of
+  // experiment described for IsDontShowOpenURLsEnabled().
+  static void RemoveItemsMatchingOpenTabs(
+      const std::set<std::string>& open_urls,
+      std::vector<InstantMostVisitedItem>* items);
+
+  // Removes URLs already open in browser, for non-1993 clients, if part of
+  // experiment described for IsDontShowOpenURLsEnabled().
+  static void RemovePageValuesMatchingOpenTabs(
+      const std::set<std::string>& open_urls,
+      base::ListValue* pages_value);
+
+ private:
+  // Helper method to log the actions carried out by the Most Visited Tile
+  // Placement experiment.
+  static void LogInHistogram(NtpTileExperimentActions action);
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(MostVisitedTilesExperiment);
+};
+
+}  // namespace history
+
+#endif  // CHROME_BROWSER_HISTORY_MOST_VISITED_TILES_EXPERIMENT_H_