Add support for variations controlled overriding UI strings to the variations service.

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 cdc1c7636823859ef53d35e49f9f5bccaddb4490..4070503c6244495596c658d7a48aa7ee63ddae8d 100644
--- a/components/variations/processed_study.h
+++ b/components/variations/processed_study.h
@@ -30,6 +30,10 @@ class ProcessedStudy {
 
   bool is_expired() const { return is_expired_; }
 
+  // Gets the index of the experiment with the given |name|. Returns -1 if no
+  // experiment is found.
+  int GetExperimentIndexByName(const std::string& name) const;
+
   static bool ValidateAndAppendStudy(
       const Study* study,
       bool is_expired,