Add UKM metric tracking for various page load metric observers.

chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer.cc

Index: chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer.cc
diff --git a/chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer.cc b/chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer.cc
index 07caa634d23e68cb717fbf8936e55971cc00a08e..7aa51cf789cd9f75139a594a537fc13523e97a46 100644
--- a/chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer.cc
+++ b/chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer.cc
@@ -4,8 +4,10 @@
 
 #include "chrome/browser/page_load_metrics/observers/service_worker_page_load_metrics_observer.h"
 
+#include "chrome/browser/browser_process.h"
 #include "chrome/browser/page_load_metrics/observers/from_gws_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/page_load_metrics_util.h"
+#include "components/ukm/public/ukm_recorder.h"
 #include "net/http/http_response_headers.h"
 #include "third_party/WebKit/public/platform/WebLoadingBehaviorFlag.h"
 
@@ -106,6 +108,8 @@ const char kHistogramNoServiceWorkerLoadSearch[] =
     "PageLoad.Clients.NoServiceWorker.DocumentTiming."
     "NavigationToLoadEventFired.search";
 
+const char kUkmServiceWorkerName[] = "ServiceWorker";
+
 }  // namespace internal
 
 namespace {
@@ -331,3 +335,15 @@ void ServiceWorkerPageLoadMetricsObserver::OnParseStart(
                         timing.parse_timing->parse_start.value());
   }
 }
+
+void ServiceWorkerPageLoadMetricsObserver::OnLoadingBehaviorObserved(
+    const page_load_metrics::PageLoadExtraInfo& info) {
+  if (!IsServiceWorkerControlled(info) || logged_ukm_event_)
+    return;
+  ukm::UkmRecorder* ukm_recorder = g_browser_process->ukm_recorder();
+  if (ukm_recorder) {
+    ukm_recorder->GetEntryBuilder(info.source_id,
+                                  internal::kUkmServiceWorkerName);
+    logged_ukm_event_ = true;
+  }
+}