[Payments]UkmSourceId() doesn't crash for JIT install PH in incognito.

This cl changes payments::ServiceWorkerPaymentApp::UkmSourceId() to
use |installable_web_app_info_->sw_scope| for JIT installable PHs while
calculating UkmSourceId.

Without this change using |stored_payment_app_info_->scope| for JIT
installable PHs would cause browser crash in incognito mode. Please
note that explicitly returning InvalidUkmSourceId for incognito
mode is not needed since UKM recorder does not record entries in
incognito mode.

Change-Id: I291d1404c89f5261e97d61ca8b74bbbfa905b229
Bug: 1066199
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2132944Reviewed-by: Danyao Wang <danyao@chromium.org>
Commit-Queue: Sahel Sharify <sahel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#756008}

components/payments/content/service_worker_payment_app.cc

@@ -533,12 +533,15 @@ void ServiceWorkerPaymentApp::OnPaymentAppIdentity(const url::Origin& origin,
 
 ukm::SourceId ServiceWorkerPaymentApp::UkmSourceId() {
   if (ukm_source_id_ == ukm::kInvalidSourceId) {
+    GURL sw_scope = needs_installation_
+                        ? GURL(installable_web_app_info_->sw_scope)
+                        : stored_payment_app_info_->scope;
     // At this point we know that the payment handler window is open for this
     // app since this getter is called for the invoked app inside the
     // PaymentRequest::OnPaymentHandlerOpenWindowCalled function.
-    ukm_source_id_ = content::PaymentAppProvider::GetInstance()
-                         ->GetSourceIdForPaymentAppFromScope(
-                             GURL(stored_payment_app_info_->scope).GetOrigin());
+    ukm_source_id_ =
+        content::PaymentAppProvider::GetInstance()
+            ->GetSourceIdForPaymentAppFromScope(sw_scope.GetOrigin());
   }
   return ukm_source_id_;
 }