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

chrome/browser/search/suggestions/suggestions_service.h

Index: chrome/browser/search/suggestions/suggestions_service.h
diff --git a/chrome/browser/search/suggestions/suggestions_service.h b/chrome/browser/search/suggestions/suggestions_service.h
index a23be99635c311d97b7618b670c843d3018a07f7..9ca2256507e3d3b5673d4fddfbb231b25a08702f 100644
--- a/chrome/browser/search/suggestions/suggestions_service.h
+++ b/chrome/browser/search/suggestions/suggestions_service.h
@@ -37,6 +37,7 @@ extern const char kSuggestionsFieldTrialURLParam[];
 extern const char kSuggestionsFieldTrialSuggestionsSuffixParam[];
 extern const char kSuggestionsFieldTrialBlacklistSuffixParam[];
 extern const char kSuggestionsFieldTrialStateParam[];
+extern const char kSuggestionsFieldTrialControlParam[];
 extern const char kSuggestionsFieldTrialStateEnabled[];
 
 // An interface to fetch server suggestions asynchronously.
@@ -51,6 +52,9 @@ class SuggestionsService : public KeyedService, public net::URLFetcherDelegate {
   // Whether this service is enabled.
   static bool IsEnabled();
 
+  // Whether the user is part of a control group.
+  static bool IsControlGroup();
+
   // Request suggestions data, which will be passed to |callback|. Initiates a
   // fetch request unless a pending one exists. To prevent multiple requests,
   // we place all |callback|s in a queue and update them simultaneously when