Refactor UKM interface for mojo-ification

chrome/browser/page_load_metrics/observers/ukm_page_load_metrics_observer.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 CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_UKM_PAGE_LOAD_METRICS_OBSERVER_H_
 #define CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_UKM_PAGE_LOAD_METRICS_OBSERVER_H_
 
 #include "base/macros.h"
 #include "base/optional.h"
 #include "base/time/time.h"
 #include "chrome/browser/page_load_metrics/page_load_metrics_observer.h"
+#include "components/ukm/ukm_service.h"
 #include "net/nqe/network_quality_estimator.h"
 #include "ui/base/page_transition_types.h"
 
 namespace content {
 class WebContents;
 }
 
 namespace internal {
 
 // Name constants are exposed here so they can be referenced from tests.
@@ skipping 58 matching lines @@
   // the URL. |app_background_time| should be set to a timestamp if the app was
   // backgrounded, otherwise it should be set to a null TimeTicks.
   void RecordPageLoadExtraInfoMetrics(
       const page_load_metrics::PageLoadExtraInfo& info,
       base::TimeTicks app_background_time);
 
   net::NetworkQualityEstimator::NetworkQualityProvider* const
       network_quality_provider_;
 
   // Unique UKM identifier for the page load we are recording metrics for.
-  const int32_t source_id_;
+  const ukm::SourceId source_id_;
 
   // Network quality estimates.
   net::EffectiveConnectionType effective_connection_type_ =
       net::EFFECTIVE_CONNECTION_TYPE_UNKNOWN;
   base::Optional<base::TimeDelta> http_rtt_estimate_;
   base::Optional<base::TimeDelta> transport_rtt_estimate_;
 
   // PAGE_TRANSITION_LINK is the default PageTransition value.
   ui::PageTransition page_transition_ = ui::PAGE_TRANSITION_LINK;
 
   DISALLOW_COPY_AND_ASSIGN(UkmPageLoadMetricsObserver);
 };
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_UKM_PAGE_LOAD_METRICS_OBSERVER_H_