Supporting study definitions without default groups and end_date filtering.

components/variations/processed_study.h

Index: components/variations/processed_study.h
diff --git a/components/variations/processed_study.h b/components/variations/processed_study.h
index 0607d064a9f307907dac756c8e9e7067447cc40d..e7807f5cf77d67deb00fd743c69cbc0217274889 100644
--- a/components/variations/processed_study.h
+++ b/components/variations/processed_study.h
@@ -18,6 +18,10 @@ class Study;
 // such as whether the study is expired and its total probability.
 class ProcessedStudy {
  public:
+  // The default group used when a study doesn't specify one. This is needed
+  // because the field trial api requires a default group name.
+  static const char kGenericDefaultExperimentName[];
+
   ProcessedStudy();
   ~ProcessedStudy();
 
@@ -43,6 +47,10 @@ class ProcessedStudy {
   // experiment is found.
   int GetExperimentIndexByName(const std::string& name) const;
 
+  // Gets the default experiment name for the study, or a generic one if none is
+  // specified.
+  const char* GetDefaultExperimentName() const;
+
   static bool ValidateAndAppendStudy(
       const Study* study,
       bool is_expired,