Add Yandex referral ID to search URL.

components/search_engines/search_terms_data.h

Index: components/search_engines/search_terms_data.h
diff --git a/components/search_engines/search_terms_data.h b/components/search_engines/search_terms_data.h
index 50f7ed2eb9391325f06b2d551cb1674f04fbc994..c72b99222f4cb7545bc1275ef2f3447945096955 100644
--- a/components/search_engines/search_terms_data.h
+++ b/components/search_engines/search_terms_data.h
@@ -61,6 +61,10 @@ class SearchTermsData {
   // GOOGLE_IMAGE_SEARCH_SOURCE.
   virtual std::string GoogleImageSearchSource() const;
 
+  // Returns the optional referral ID to be passed to Yandex when searching from
+  // the omnibox (returns the empty string if not supported/applicable).
+  virtual std::string GetYandexReferralID() const;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(SearchTermsData);
 };