Revert of Supporting study definitions without default groups and end_date filtering.

components/variations/study_filtering.cc

Index: components/variations/study_filtering.cc
diff --git a/components/variations/study_filtering.cc b/components/variations/study_filtering.cc
index 510925132e1b1be266624727f4d7e9572862b89f..159b544f4e7d388e0fc3c49d251a82e8381af48a 100644
--- a/components/variations/study_filtering.cc
+++ b/components/variations/study_filtering.cc
@@ -143,16 +143,6 @@
   return true;
 }
 
-bool CheckStudyEndDate(const Study_Filter& filter,
-                       const base::Time& date_time) {
-  if (filter.has_end_date()) {
-    const base::Time end_date = ConvertStudyDateToBaseTime(filter.end_date());
-    return end_date >= date_time;
-  }
-
-  return true;
-}
-
 bool CheckStudyVersion(const Study_Filter& filter,
                        const base::Version& version) {
   if (filter.has_min_version()) {
@@ -232,11 +222,6 @@
     if (!CheckStudyStartDate(study.filter(), reference_date)) {
       DVLOG(1) << "Filtered out study " << study.name() <<
                   " due to start date.";
-      return false;
-    }
-
-    if (!CheckStudyEndDate(study.filter(), reference_date)) {
-      DVLOG(1) << "Filtered out study " << study.name() << " due to end date.";
       return false;
     }