[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 d4e47452c8498f4857c595f9f96d5118654bbe6f..ff9eab82cea9f7998c851621b8a9a665222d3d42 100644
--- a/chrome/browser/search/suggestions/suggestions_service.cc
+++ b/chrome/browser/search/suggestions/suggestions_service.cc
@@ -80,6 +80,7 @@ const char kSuggestionsFieldTrialSuggestionsSuffixParam[] =
     "suggestions_suffix";
 const char kSuggestionsFieldTrialBlacklistSuffixParam[] = "blacklist_suffix";
 const char kSuggestionsFieldTrialStateParam[] = "state";
+const char kSuggestionsFieldTrialControlParam[] = "control";
 const char kSuggestionsFieldTrialStateEnabled[] = "enabled";
 
 SuggestionsService::SuggestionsService(
@@ -105,6 +106,12 @@ 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));