[Play Billing] Update helper to stay in sync with ARC++.

Update WebPaymentIntentHelper to stay in sync with the copy in ARC++.
This CL pulls out the extraction of payment intent details to a new
method so that ARC++ can use it synchronously.

Bug: 1109119
Change-Id: Ic0c784a3fc51ed853ef51e0535c51b6b3fb06b60
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2352259Reviewed-by: Rouslan Solomakhin <rouslan@chromium.org>
Commit-Queue: Jeevan Shikaram <jshikaram@chromium.org>
Cr-Commit-Position: refs/heads/master@{#798038}

components/payments/content/android/java/src/org/chromium/components/payments/intent/WebPaymentIntentHelper.java

@@ -95,6 +95,22 @@ public class WebPaymentIntentHelper {
         void onPaymentSuccess(String methodName, String details, PayerData payerData);
     }
 
+    /**
+     * Get stringified payment details from a payment intent.
+     *
+     * @param data The payment intent data.
+     * @return The stringified payment details, if any.
+     */
+    @Nullable
+    public static String getPaymentIntentDetails(Intent data) {
+        String details = data.getExtras().getString(EXTRA_RESPONSE_DETAILS);
+        if (details == null) {
+            // try to get deprecated details rather than early returning.
+            details = data.getExtras().getString(EXTRA_DEPRECATED_RESPONSE_INSTRUMENT_DETAILS);
+        }
+        return details;
+    }
+
     /**
      * Parse the Payment Intent response.
      * @param resultCode Result code of the requested intent.
@@ -125,11 +141,7 @@ public class WebPaymentIntentHelper {
             return;
         }
 
-        String details = data.getExtras().getString(EXTRA_RESPONSE_DETAILS);
-        if (details == null) {
-            // try to get deprecated details rather than early returning.
-            details = data.getExtras().getString(EXTRA_DEPRECATED_RESPONSE_INSTRUMENT_DETAILS);
-        }
+        String details = getPaymentIntentDetails(data);
         if (TextUtils.isEmpty(details)) {
             errorCallback.onPaymentError(ErrorStrings.MISSING_DETAILS_FROM_PAYMENT_APP);
             return;