[Payments] Use event to log checkout funnel metrics.

components/payments/core/journey_logger.h

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_PAYMENTS_CORE_JOURNEY_LOGGER_H_
 #define COMPONENTS_PAYMENTS_CORE_JOURNEY_LOGGER_H_
 
 #include <string>
 
 #include "base/macros.h"
@@ skipping 118 matching lines @@
           number_suggestions_shown_(0),
           is_requested_(false) {}
 
     int number_selection_adds_;
     int number_selection_changes_;
     int number_selection_edits_;
     int number_suggestions_shown_;
     bool is_requested_;
   };
 
+  // Records the histograms for all the steps of a successful checkout flow

[gogerald1, 2017/05/19 19:42:17]

nit: *a complete*

+  // that were reached.
+  void RecordCheckoutFlowMetrics();
+
   // Records the histograms for all the sections that were requested by the
   // merchant.
   void RecordSectionSpecificStats(CompletionStatus completion_status);
 
   // Records the metrics related the the CanMakePayment method unless in
   // incognito mode.
   void RecordCanMakePaymentStats(CompletionStatus completion_status);
 
   // Records CanMakePayment's return value effect on whether the Payment Request
   // was shown or not.
@@ skipping 21 matching lines @@
 
   // Not owned, will outlive this object.
   ukm::UkmService* ukm_service_;
 
   DISALLOW_COPY_AND_ASSIGN(JourneyLogger);
 };
 
 }  // namespace payments
 
 #endif  // COMPONENTS_PAYMENTS_CORE_JOURNEY_LOGGER_H_