Eliminate NOTIFICATION_HISTORY_LOADED notification

chrome/browser/safe_browsing/incident_reporting/last_download_finder.h

Index: chrome/browser/safe_browsing/incident_reporting/last_download_finder.h
diff --git a/chrome/browser/safe_browsing/incident_reporting/last_download_finder.h b/chrome/browser/safe_browsing/incident_reporting/last_download_finder.h
index 233773be4426e7b8a02ba1fc0eb4d54da6ee986f..54e4b5a5a470ee3db6d4109df90c16cb25c03c07 100644
--- a/chrome/browser/safe_browsing/incident_reporting/last_download_finder.h
+++ b/chrome/browser/safe_browsing/incident_reporting/last_download_finder.h
@@ -12,7 +12,9 @@
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
+#include "base/scoped_observer.h"
 #include "chrome/browser/history/download_row.h"
+#include "components/history/core/browser/history_service_observer.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
@@ -34,7 +36,8 @@ class ClientIncidentReport_DownloadDetails;
 
 // Finds the most recent executable downloaded by any on-the-record profile with
 // history that participates in safe browsing.
-class LastDownloadFinder : public content::NotificationObserver {
+class LastDownloadFinder : public content::NotificationObserver,
+                           public history::HistoryServiceObserver {
  public:
   // The type of a callback run by the finder upon completion. The argument is a
   // protobuf containing details of the download that was found, or an empty
@@ -52,6 +55,9 @@ class LastDownloadFinder : public content::NotificationObserver {
   static scoped_ptr<LastDownloadFinder> Create(
       const LastDownloadCallback& callback);
 
+  // history::HistoryServiceObserver:
+  void OnHistoryServiceLoaded(HistoryService* service) override;
+
  protected:
   // Protected constructor so that unit tests can create a fake finder.
   LastDownloadFinder();
@@ -109,6 +115,10 @@ class LastDownloadFinder : public content::NotificationObserver {
   // A factory for asynchronous operations on profiles' HistoryService.
   base::WeakPtrFactory<LastDownloadFinder> weak_ptr_factory_;
 
+  // HistoryServiceObserver
+  ScopedObserver<HistoryService, HistoryServiceObserver>
+      history_service_observer_;
+
   DISALLOW_COPY_AND_ASSIGN(LastDownloadFinder);
 };