[Payment Request] Fixes a bug with the serialized PaymentResponse.details

PaymentResponse.details was being JSON-escaped twice.

Bug: 602666
Change-Id: I0b574654353b25ed16d3baf143ac12ac14526953
Reviewed-on: https://chromium-review.googlesource.com/565008
Commit-Queue: mahmadi <mahmadi@chromium.org>
Reviewed-by: Mathieu Perreault <mathp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#485373}

ios/web/payments/payment_request.cc

@@ -4,6 +4,7 @@
 
 #include "ios/web/public/payments/payment_request.h"
 
+#include "base/json/json_reader.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
 
@@ -362,7 +363,13 @@ std::unique_ptr<base::DictionaryValue> PaymentResponse::ToDictionaryValue()
 
   result->SetString(kPaymentRequestId, this->payment_request_id);
   result->SetString(kPaymentResponseMethodName, this->method_name);
-  result->SetString(kPaymentResponseDetails, this->details);
+  // |this.details| is a json-serialized string. Parse it to a base::Value so
+  // that when |this| is converted to a JSON string, |this.details| won't get
+  // json-escaped.
+  std::unique_ptr<base::Value> details =
+      base::JSONReader().ReadToValue(this->details);
+  if (details)
+    result->Set(kPaymentResponseDetails, std::move(details));
   if (!this->shipping_address.ToDictionaryValue()->empty()) {
     result->Set(kPaymentResponseShippingAddress,
                 this->shipping_address.ToDictionaryValue());

ios/web/payments/payment_request_unittest.cc

@@ -264,7 +264,6 @@ TEST(PaymentRequestTest, ParsingFullyPopulatedRequestDictionarySucceeds) {
 TEST(PaymentRequestTest, EmptyResponseDictionary) {
   base::DictionaryValue expected_value;
 
-  expected_value.SetString("details", "");
   expected_value.SetString("paymentRequestID", "");
   expected_value.SetString("methodName", "");
 
@@ -288,9 +287,7 @@ TEST(PaymentRequestTest, PopulatedResponseDictionary) {
       new base::DictionaryValue);
   billing_address->SetString("postalCode", "90210");
   details->Set("billingAddress", std::move(billing_address));
-  std::string stringified_details;
-  base::JSONWriter::Write(*details, &stringified_details);
-  expected_value.SetString("details", stringified_details);
+  expected_value.Set("details", std::move(details));
   expected_value.SetString("paymentRequestID", "12345");
   expected_value.SetString("methodName", "American Express");
   std::unique_ptr<base::DictionaryValue> shipping_address(

ios/web/public/payments/payment_request.h

@@ -262,8 +262,8 @@ class PaymentResponse {
   // to fulfil the transaction.
   base::string16 method_name;
 
-  // A credit card response object used by the merchant to process the
-  // transaction and determine successful fund transfer.
+  // The json-serialized stringified details of the payment method. Used by the
+  // merchant to process the transaction and determine successful fund transfer.
   std::string details;
 
   // If request_shipping was set to true in the PaymentOptions passed to the