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

chrome/browser/search/suggestions/suggestions_service.cc

Index: chrome/browser/search/suggestions/suggestions_service.cc
diff --git a/chrome/browser/search/suggestions/suggestions_service.cc b/chrome/browser/search/suggestions/suggestions_service.cc
index 04f6a61aab6a222113fa3772e018ebe6bcca79c3..3277f5e82cb91e0f8e3dabd7d997f770699465b9 100644
--- a/chrome/browser/search/suggestions/suggestions_service.cc
+++ b/chrome/browser/search/suggestions/suggestions_service.cc
@@ -79,6 +79,7 @@ const char kSuggestionsFieldTrialSuggestionsSuffixParam[] =
     "suggestions_suffix";
 const char kSuggestionsFieldTrialBlacklistSuffixParam[] = "blacklist_suffix";
 const char kSuggestionsFieldTrialStateParam[] = "state";
+const char kSuggestionsFieldTrialControlParam[] = "control";
 const char kSuggestionsFieldTrialStateEnabled[] = "enabled";
 const char kSuggestionsFieldTrialTimeoutMs[] = "timeout_ms";
 
@@ -111,6 +112,12 @@ bool SuggestionsService::IsEnabled() {
          kSuggestionsFieldTrialStateEnabled;
 }
 
+// static
+bool SuggestionsService::IsControlGroup() {
+  return GetExperimentParam(kSuggestionsFieldTrialControlParam) ==
+         kSuggestionsFieldTrialStateEnabled;
+}
+
 void SuggestionsService::FetchSuggestionsData(
     SuggestionsService::ResponseCallback callback) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));