PaymentApp: Implement InvokePaymentApp() in browser side.

content/browser/service_worker/service_worker_metrics.cc

Index: content/browser/service_worker/service_worker_metrics.cc
diff --git a/content/browser/service_worker/service_worker_metrics.cc b/content/browser/service_worker/service_worker_metrics.cc
index aca38b992cbb47ccc9902e4dd28fab7141eba192..76b97a3163d1fe5e9f59776c84bd4ff89f83f89a 100644
--- a/content/browser/service_worker/service_worker_metrics.cc
+++ b/content/browser/service_worker/service_worker_metrics.cc
@@ -80,6 +80,8 @@ std::string EventTypeToSuffix(ServiceWorkerMetrics::EventType event_type) {
       return "_NAVIGATION_HINT_LINK_TAP_DOWN";
     case ServiceWorkerMetrics::EventType::EXTERNAL_REQUEST:
       return "_EXTERNAL_REQUEST";
+    case ServiceWorkerMetrics::EventType::PAYMENT_REQUEST:
+      return "_PAYMENT_REQUEST";
     case ServiceWorkerMetrics::EventType::NUM_TYPES:
       NOTREACHED() << static_cast<int>(event_type);
   }
@@ -231,6 +233,8 @@ const char* ServiceWorkerMetrics::EventTypeToString(EventType event_type) {
       return "Navigation Hint Link Tap Down";
     case EventType::EXTERNAL_REQUEST:
       return "External Request";
+    case EventType::PAYMENT_REQUEST:
+      return "Payment Request";
     case EventType::NUM_TYPES:
       break;
   }
@@ -587,6 +591,8 @@ void ServiceWorkerMetrics::RecordEventDuration(EventType event,
     case EventType::EXTERNAL_REQUEST:
       UMA_HISTOGRAM_MEDIUM_TIMES("ServiceWorker.ExternalRequest.Time", time);
       break;
+    case EventType::PAYMENT_REQUEST:

[nhiroki, 2017/01/12 03:12:37]

To identify which event takes long time, having a UMA of event duration is good.
Can you add a TODO comment like this?

TODO(zino): Add event duration UMA for PaymentRequest API.

[zino, 2017/01/13 16:41:11]

I just updated the C++ codes and histograms.xml.

+      break;
     // Those navigation hints should not be sent as request events.
     case EventType::NAVIGATION_HINT_LINK_MOUSE_DOWN:
     case EventType::NAVIGATION_HINT_LINK_TAP_UNCONFIRMED: