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

components/variations/processed_study.cc

Index: components/variations/processed_study.cc
diff --git a/components/variations/processed_study.cc b/components/variations/processed_study.cc
index 10a1bd78ed409dd404179f2365c869d2c0ae877b..8c1f8d0f8a1cd6852cd2fb234dbec9267b4f8710 100644
--- a/components/variations/processed_study.cc
+++ b/components/variations/processed_study.cc
@@ -21,6 +21,11 @@
     base::FieldTrial::Probability* total_probability,
     bool* all_assignments_to_one_group,
     std::string* single_feature_name) {
+  // At the moment, a missing default_experiment_name makes the study invalid.
+  if (study.default_experiment_name().empty()) {
+    DVLOG(1) << study.name() << " has no default experiment defined.";
+    return false;
+  }
   if (study.filter().has_min_version() &&
       !base::Version::IsValidWildcardString(study.filter().min_version())) {
     DVLOG(1) << study.name() << " has invalid min version: "
@@ -87,11 +92,9 @@
       found_default_group = true;
   }
 
-  // Specifying a default experiment is optional, so finding it in the
-  // experiment list is only required when it is specified.
-  if (!study.default_experiment_name().empty() && !found_default_group) {
-    DVLOG(1) << study.name() << " is missing default experiment ("
-             << study.default_experiment_name() << ") in its experiment list";
+  if (!found_default_group) {
+    DVLOG(1) << study.name() << " is missing default experiment in its "
+             << "experiment list";
     // The default group was not found in the list of groups. This study is not
     // valid.
     return false;
@@ -109,10 +112,6 @@
 
 
 }  // namespace
-
-// static
-const std::string ProcessedStudy::kGenericDefaultExperimentName =
-    "VariationsDefaultExperiment";
 
 ProcessedStudy::ProcessedStudy()
     : study_(NULL),
@@ -151,13 +150,6 @@
   return -1;
 }
 
-const std::string& ProcessedStudy::GetDefaultExperimentName() const {
-  if (study_->default_experiment_name().empty())
-    return kGenericDefaultExperimentName;
-
-  return study_->default_experiment_name();
-}
-
 // static
 bool ProcessedStudy::ValidateAndAppendStudy(
     const Study* study,