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

components/ntp_tiles/metrics.h

Index: components/ntp_tiles/metrics.h
diff --git a/components/ntp_tiles/metrics.h b/components/ntp_tiles/metrics.h
index c32dbf258df3a21c54958841bd61274cf2120c98..1b1a00ffd899154fcd06c5f42f04a97faa35b614 100644
--- a/components/ntp_tiles/metrics.h
+++ b/components/ntp_tiles/metrics.h
@@ -9,6 +9,11 @@
 #include <vector>
 
 #include "components/ntp_tiles/ntp_tile.h"
+#include "url/gurl.h"
+
+namespace rappor {
+class RapporService;
+}  // namespace rappor
 
 namespace ntp_tiles {
 namespace metrics {
@@ -39,10 +44,17 @@ enum MostVisitedTileType {
   UNKNOWN_TILE_TYPE,
 };
 
+struct TileImpression {
+  NTPTileSource source;
+  MostVisitedTileType type;
+  GURL url;

[Marc Treib, 2016/12/08 12:58:22]

Add a constructor? As it is, it's easy to accidentally leave |source|
uninitialized. (In most places where these are constructed, you can then use
emplace_back, so it won't be any less convenient)

[mastiz, 2016/12/08 13:47:07]

Done.

+};
+
 // 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,