Retire ScopedObserver in /components/ntp_tiles.

ScopedObserver is being deprecated in favor of two new classes:
- base::ScopedObservation for observers that only ever observe
  a single source.
- base::ScopedMultiSourceObservation for observers that do or may
  observe more than a single source.

This CL was uploaded by git cl split.

R=aee@chromium.org

Bug: 1145565
Change-Id: I48d7536ee7228fb3888849c7b2e4c82523bcd230
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2532956
Commit-Queue: Sigurður Ásgeirsson <siggi@chromium.org>
Auto-Submit: Sigurður Ásgeirsson <siggi@chromium.org>
Reviewed-by: Esmael Elmoslimany <aee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#826818}

components/ntp_tiles/custom_links_manager_impl.cc

@@ -20,10 +20,10 @@ namespace ntp_tiles {
 CustomLinksManagerImpl::CustomLinksManagerImpl(
     PrefService* prefs,
     history::HistoryService* history_service)
-    : prefs_(prefs), store_(prefs), history_service_observer_(this) {
+    : prefs_(prefs), store_(prefs) {
   DCHECK(prefs);
   if (history_service)
-    history_service_observer_.Add(history_service);
+    history_service_observation_.Observe(history_service);
   if (IsInitialized())
     current_links_ = store_.RetrieveLinks();
 
@@ -226,7 +226,7 @@ void CustomLinksManagerImpl::OnURLsDeleted(
 
 void CustomLinksManagerImpl::HistoryServiceBeingDeleted(
     history::HistoryService* history_service) {
-  history_service_observer_.RemoveAll();
+  history_service_observation_.RemoveObservation();
 }
 
 void CustomLinksManagerImpl::OnPreferenceChanged() {

components/ntp_tiles/custom_links_manager_impl.h

@@ -11,7 +11,7 @@
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/optional.h"
-#include "base/scoped_observer.h"
+#include "base/scoped_observation.h"
 #include "components/history/core/browser/history_service.h"
 #include "components/history/core/browser/history_service_observer.h"
 #include "components/ntp_tiles/custom_links_manager.h"
@@ -95,8 +95,9 @@ class CustomLinksManagerImpl : public CustomLinksManager,
   base::CallbackList<void()> callback_list_;
 
   // Observer for the HistoryService.
-  ScopedObserver<history::HistoryService, history::HistoryServiceObserver>
-      history_service_observer_;
+  base::ScopedObservation<history::HistoryService,
+                          history::HistoryServiceObserver>
+      history_service_observation_{this};
 
   // Observer for Chrome sync changes to |prefs::kCustomLinksList| and
   // |prefs::kCustomLinksInitialized|.

components/ntp_tiles/most_visited_sites.cc

@@ -218,11 +218,11 @@ void MostVisitedSites::SetMostVisitedURLsObserver(Observer* observer,
   if (top_sites_) {
     // Register as TopSitesObserver so that we can update ourselves when the
     // TopSites changes.
-    top_sites_observer_.Observe(top_sites_.get());
+    top_sites_observation_.Observe(top_sites_.get());
   }
 
   if (repeatable_queries_) {
-    repeatable_queries_observer_.Observe(repeatable_queries_);
+    repeatable_queries_observation_.Observe(repeatable_queries_);
   }
 
   if (custom_links_) {
@@ -947,7 +947,7 @@ void MostVisitedSites::OnRepeatableQueriesUpdated() {
 }
 
 void MostVisitedSites::OnRepeatableQueriesServiceShuttingDown() {
-  repeatable_queries_observer_.RemoveObservation();
+  repeatable_queries_observation_.RemoveObservation();
 }
 
 bool MostVisitedSites::ShouldAddHomeTile() const {

components/ntp_tiles/most_visited_sites.h

@@ -380,11 +380,11 @@ class MostVisitedSites : public history::TopSitesObserver,
       suggestions_subscription_;
 
   base::ScopedObservation<history::TopSites, history::TopSitesObserver>
-      top_sites_observer_{this};
+      top_sites_observation_{this};
 
   base::ScopedObservation<RepeatableQueriesService,
                           RepeatableQueriesServiceObserver>
-      repeatable_queries_observer_{this};
+      repeatable_queries_observation_{this};
 
   std::unique_ptr<base::CallbackList<void()>::Subscription>
       custom_links_subscription_;