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

chrome/browser/android/most_visited_sites.h

Index: chrome/browser/android/most_visited_sites.h
diff --git a/chrome/browser/android/most_visited_sites.h b/chrome/browser/android/most_visited_sites.h
index a228d1608d78076aca693ca1412b2d521948aff8..8e1137c2d53c73baf2e190fbc491598b8f6059bc 100644
--- a/chrome/browser/android/most_visited_sites.h
+++ b/chrome/browser/android/most_visited_sites.h
@@ -98,6 +98,9 @@ class MostVisitedSites : public content::NotificationObserver {
   // The maximum number of most visited sites to return.
   int num_sites_;
 
+  // Whether the user is in a control group for the purposes of logging.
+  bool is_control_group_;
+
   // Counters for UMA metrics.
 
   // Number of tiles using a local thumbnail image for this NTP session.