Remove deprecated version of PaymentResponse::ToDictionaryValue.

This is no longer in use as of
https://chromereviews.googleplex.com/494267014/.

BUG=602666

Review-Url: https://codereview.chromium.org/2333483002
Cr-Commit-Position: refs/heads/master@{#417963}

ios/web/payments/payment_request.cc

@@ -334,8 +334,4 @@ std::unique_ptr<base::DictionaryValue> PaymentResponse::ToDictionaryValue()
   return result;
 }
 
-void PaymentResponse::ToDictionaryValue(base::DictionaryValue* value) const {
-  value->MergeDictionary(ToDictionaryValue().get());
-}
-
 }  // namespace web

ios/web/public/payments/payment_request.h

@@ -315,9 +315,6 @@ class PaymentResponse {
   // Populates |value| with the properties of this PaymentResponse.
   std::unique_ptr<base::DictionaryValue> ToDictionaryValue() const;
 
-  // TODO(jdonnelly): Remove this after removing downstream use.
-  void ToDictionaryValue(base::DictionaryValue* value) const;
-
   // The payment method identifier for the payment method that the user selected
   // to fulfil the transaction.
   base::string16 method_name;