PaymentApp: Implement InvokePaymentApp() in browser side.

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 60a9dfa6cdecc1f1798b3f2f467bd6928f4d65cf..2bdd8414edba55f78f0a490ab1240cb4588c1536 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -59745,6 +59745,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Counts page loads controlled by a service worker.</summary>
 </histogram>
 
+<histogram name="ServiceWorker.PaymentRequestEvent.Time" units="ms">
+  <owner>jinho.bang@samsung.com</owner>
+  <summary>
+    The time taken between dispatching an PaymentRequestEvent to a Service
+    Worker and receiving a message that it finished handling the event. Includes
+    the time for the waitUntil() promise to settle.
+  </summary>
+</histogram>
+
 <histogram name="ServiceWorker.PushEvent.Time" units="ms">
   <owner>johnme@chromium.org</owner>
   <summary>
@@ -103679,6 +103688,8 @@ value.
   <int value="18" label="NAVIGATION_HINT_LINK_MOUSE_DOWN"/>
   <int value="19" label="NAVIGATION_HINT_LINK_TAP_UNCONFIRMED"/>
   <int value="20" label="NAVIGATION_HINT_LINK_TAP_DOWN"/>
+  <int value="21" label="EXTERNAL_REQUEST"/>
+  <int value="22" label="PAYMENT_REQUEST"/>
 </enum>
 
 <enum name="ServiceWorkerReadResponseResult" type="int">