[Payments] Add PaymentRequest checkout funnel UKMs.

tools/metrics/ukm/ukm.xml

Index: tools/metrics/ukm/ukm.xml
diff --git a/tools/metrics/ukm/ukm.xml b/tools/metrics/ukm/ukm.xml
index d85419eaeeba44a8fe246c4eeb8ca5eb50af2b47..e83eafe975b032bcdbfc7e19f024ab2cdf793db6 100644
--- a/tools/metrics/ukm/ukm.xml
+++ b/tools/metrics/ukm/ukm.xml
@@ -11,6 +11,15 @@ along with a detailed description for each metric.
 
 <ukm-configuration>
 
+<event name="Autofill.CardUploadDecision">
+  <owner>sebsg@chromium.org</owner>
+  <metric name="UploadDecision">
+    <summary>
+      Whether the upload was proposed to the user or the reason why it was not.
+    </summary>
+  </metric>
+</event>
+
 <event name="PageLoad">
   <owner>bmcquade@chromium.org</owner>
   <summary>
@@ -36,9 +45,21 @@ along with a detailed description for each metric.
   </metric>
 </event>
 
-<event name="Autofill.CardUploadDecision">
+<event name="PaymentRequest.CheckoutEvents">
   <owner>sebsg@chromium.org</owner>
-  <metric name="UploadDecision"/>
+  <metric name="CompletionsStatus">
+    <summary>
+      How the Payment Request ended. Values defined in the CompletionStatus enum
+      of components/payments/core/journey_logger.h.
+    </summary>
+  </metric>
+  <metric name="Events">
+    <summary>
+      Bitfield representing the events that occurred during the Payment Request.
+      Values defined in the Event enum of
+      components/payments/core/journey_logger.h.
+    </summary>
+  </metric>
 </event>
 
 <event name="Translate">