[PaymentReqeust] Add error message in PaymentDetails. (in blink side)

third_party/WebKit/Source/modules/payments/PaymentsValidators.h

Index: third_party/WebKit/Source/modules/payments/PaymentsValidators.h
diff --git a/third_party/WebKit/Source/modules/payments/PaymentsValidators.h b/third_party/WebKit/Source/modules/payments/PaymentsValidators.h
index 6ee2499f214f664705657ea20ee08977034967a2..e2bbedc8d4aff86026b69357396ee63c7b1d0249 100644
--- a/third_party/WebKit/Source/modules/payments/PaymentsValidators.h
+++ b/third_party/WebKit/Source/modules/payments/PaymentsValidators.h
@@ -38,6 +38,9 @@ public:
     //  - Has a valid script code, if any.
     // A script code should be present only if language code is present.
     static bool isValidShippingAddress(const mojom::blink::PaymentAddressPtr&, String* optionalErrorMessage);
+
+    // Returns false if |error| is too long (greater than 2048).
+    static bool isValidErrorMsgFormat(const String& code, String* optionalErrorMessage);
 };
 
 } // namespace blink