ntp_tiles::metrics: Add rappor metrics for impression URLs per icon type.

components/ntp_tiles/metrics.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 COMPONENTS_NTP_TILES_METRICS_H_
 #define COMPONENTS_NTP_TILES_METRICS_H_
 
 #include <utility>
 #include <vector>
 
 #include "components/ntp_tiles/ntp_tile.h"
+#include "url/gurl.h"
+
+namespace rappor {
+class RapporService;
+}  // namespace rappor
 
 namespace ntp_tiles {
 namespace metrics {
 
 // The visual type of a most visited tile.
 //
 // These values must stay in sync with the MostVisitedTileType enum
 // in histograms.xml.
 //
 // A Java counterpart will be generated for this enum.
@@ skipping 10 matching lines @@
   // The number of different tile types that get recorded. Entries below this
   // are not recorded in UMA.
   NUM_RECORDED_TILE_TYPES,
   // The item displays a thumbnail of the page. Used on desktop.
   THUMBNAIL,
   // The tile type has not been determined yet. Used on iOS, until we can detect
   // when all tiles have loaded.
   UNKNOWN_TILE_TYPE,
 };
 
+struct TileImpression {
+  TileImpression(NTPTileSource source,
+                 MostVisitedTileType type,
+                 const GURL& url)
+      : source(source), type(type), url(url) {}
+
+  NTPTileSource source;
+  MostVisitedTileType type;
+  GURL url;
+};
+
 // Records an NTP impression, after all tiles have loaded.
-// Includes the visual types (see above) of all visible tiles.
-void RecordPageImpression(
-    const std::vector<std::pair<NTPTileSource, MostVisitedTileType>>& tiles);
+// Includes the visual types (see above) of all visible tiles. If
+// |rappor_service| is null, no rappor metrics will be reported.
+void RecordPageImpression(const std::vector<TileImpression>& tiles,
+                          rappor::RapporService* rappor_service);
 
 // Records a click on a tile.
 void RecordTileClick(int index,
                      NTPTileSource source,
                      MostVisitedTileType tile_type);
 
 }  // namespace metrics
 }  // namespace ntp_tiles
 
 #endif