[Payment Request] Update the CurrencyStringFormatter to call the native impl.

components/payments/currency_formatter.h

Index: components/payments/currency_formatter.h
diff --git a/components/payments/currency_formatter.h b/components/payments/currency_formatter.h
index 06695a8479152385c5f30acfff5dd90df3fbd4ba..2794b37dccec65344dd464477185ae63e976f669 100644
--- a/components/payments/currency_formatter.h
+++ b/components/payments/currency_formatter.h
@@ -41,9 +41,14 @@ class CurrencyFormatter {
   // formatter, this method will return |amount|.
   base::string16 Format(const std::string& amount);
 
+  // Returns the formatted currency code (<= 6 characters including ellipsis if
+  // applicable).
+  std::string formatted_currency_code() { return formatted_currency_code_; }
+
  private:
   const icu::Locale locale_;
   std::unique_ptr<icu::UnicodeString> currency_code_;
+  std::string formatted_currency_code_;
   std::unique_ptr<icu::NumberFormat> icu_formatter_;
 
   DISALLOW_COPY_AND_ASSIGN(CurrencyFormatter);