[Android NTP] Logging histograms for users that are part of a control group.

chrome/browser/android/most_visited_sites.cc

Index: chrome/browser/android/most_visited_sites.cc
diff --git a/chrome/browser/android/most_visited_sites.cc b/chrome/browser/android/most_visited_sites.cc
index 5eda3f36fa71b09f5ec6c82af16507cb240cd7d6..16aed52297656e67f8d3885362bbe3726f857b8c 100644
--- a/chrome/browser/android/most_visited_sites.cc
+++ b/chrome/browser/android/most_visited_sites.cc
@@ -58,6 +58,8 @@ const char kNumEmptyTilesHistogramName[] = "NewTabPage.NumberOfGrayTiles";
 const char kNumServerTilesHistogramName[] = "NewTabPage.NumberOfExternalTiles";
 // Client suggestion opened.
 const char kOpenedItemClientHistogramName[] = "NewTabPage.MostVisited.client";
+// Control group suggestion opened.
+const char kOpenedItemControlHistogramName[] = "NewTabPage.MostVisited.client0";
 // Server suggestion opened, no provider.
 const char kOpenedItemServerHistogramName[] = "NewTabPage.MostVisited.server";
 // Server suggestion opened with provider.
@@ -66,6 +68,9 @@ const char kOpenedItemServerProviderHistogramFormat[] =
 // Client impression.
 const char kImpressionClientHistogramName[] =
     "NewTabPage.SuggestionsImpression.client";
+// Control group impression.
+const char kImpressionControlHistogramName[] =
+    "NewTabPage.SuggestionsImpression.client0";
 // Server suggestion impression, no provider.
 const char kImpressionServerHistogramName[] =
     "NewTabPage.SuggestionsImpression.server";
@@ -168,8 +173,9 @@ void LogHistogramEvent(const std::string& histogram, int position,
 }  // namespace
 
 MostVisitedSites::MostVisitedSites(Profile* profile)
-    : profile_(profile), num_sites_(0), num_local_thumbs_(0),
-      num_server_thumbs_(0), num_empty_thumbs_(0), weak_ptr_factory_(this) {
+    : profile_(profile), num_sites_(0), is_control_group_(false),
+      num_local_thumbs_(0), num_server_thumbs_(0), num_empty_thumbs_(0),
+      weak_ptr_factory_(this) {
   // Register the debugging page for the Suggestions Service and the thumbnails
   // debugging page.
   content::URLDataSource::Add(profile_,
@@ -278,7 +284,9 @@ void MostVisitedSites::RecordOpenedMostVisitedItem(JNIEnv* env,
                                                    jint index) {
   switch (mv_source_) {
     case TOP_SITES: {
-      UMA_HISTOGRAM_SPARSE_SLOWLY(kOpenedItemClientHistogramName, index);
+      const std::string histogram = is_control_group_ ?
+          kOpenedItemControlHistogramName : kOpenedItemClientHistogramName;
+      LogHistogramEvent(histogram, index, num_sites_);
       break;
     }
     case SUGGESTIONS_SERVICE: {
@@ -354,8 +362,10 @@ void MostVisitedSites::OnMostVisitedURLsAvailable(
 
   int num_tiles = urls.size();
   UMA_HISTOGRAM_SPARSE_SLOWLY(kNumTilesHistogramName, num_tiles);
+  const std::string histogram = is_control_group_ ?
+      kImpressionControlHistogramName : kImpressionClientHistogramName;
   for (int i = 0; i < num_tiles; ++i) {
-    UMA_HISTOGRAM_SPARSE_SLOWLY(kImpressionClientHistogramName, i);
+    LogHistogramEvent(histogram, i, num_sites_);
   }
 
   JNIEnv* env = AttachCurrentThread();
@@ -370,8 +380,14 @@ void MostVisitedSites::OnSuggestionsProfileAvailable(
     ScopedJavaGlobalRef<jobject>* j_observer,
     const SuggestionsProfile& suggestions_profile) {
   int size = suggestions_profile.suggestions_size();
-  if (size == 0) {
-    // No suggestions data available, initiate Top Sites query.
+
+  // Determine if the user is in a control group (they would have received
+  // suggestions, but are in a group where they shouldn't).
+  is_control_group_ = size && SuggestionsService::IsControlGroup();
+
+  // If no suggestions data is available or the user is in a control group,
+  // initiate Top Sites query.
+  if (is_control_group_ || !size) {
     InitiateTopSitesQuery();
     return;
   }