Retire ScopedObserver in /components/ntp_snippets.

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=harringtond@chromium.org

Bug: 1145565
Change-Id: I00ea07dd484293ba9cc164f97838def2a4e15615
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2532657
Auto-Submit: Sigurður Ásgeirsson <siggi@chromium.org>
Reviewed-by: Dan H <harringtond@chromium.org>
Commit-Queue: Dan H <harringtond@chromium.org>
Cr-Commit-Position: refs/heads/master@{#826371}

components/ntp_snippets/content_suggestions_service.cc

@@ -56,8 +56,6 @@ ContentSuggestionsService::ContentSuggestionsService(
     std::unique_ptr<UserClassifier> user_classifier,
     std::unique_ptr<RemoteSuggestionsScheduler> remote_suggestions_scheduler)
     : state_(state),
-      identity_manager_observer_(this),
-      history_service_observer_(this),
       remote_suggestions_provider_(nullptr),
       large_icon_service_(large_icon_service),
       pref_service_(pref_service),
@@ -66,11 +64,11 @@ ContentSuggestionsService::ContentSuggestionsService(
       category_ranker_(std::move(category_ranker)) {
   // Can be null in tests.
   if (identity_manager) {
-    identity_manager_observer_.Add(identity_manager);
+    identity_manager_observation_.Observe(identity_manager);
   }
 
   if (history_service) {
-    history_service_observer_.Add(history_service);
+    history_service_observation_.Observe(history_service);
   }
 
   RestoreDismissedCategoriesFromPrefs();
@@ -552,7 +550,8 @@ void ContentSuggestionsService::OnURLsDeleted(
 
 void ContentSuggestionsService::HistoryServiceBeingDeleted(
     history::HistoryService* history_service) {
-  history_service_observer_.RemoveAll();
+  DCHECK(history_service_observation_.IsObservingSource(history_service));
+  history_service_observation_.RemoveObservation();
 }
 
 bool ContentSuggestionsService::TryRegisterProviderForCategory(

components/ntp_snippets/content_suggestions_service.h

@@ -14,7 +14,7 @@
 #include "base/callback_forward.h"
 #include "base/observer_list.h"
 #include "base/optional.h"
-#include "base/scoped_observer.h"
+#include "base/scoped_observation.h"
 #include "base/task/cancelable_task_tracker.h"
 #include "base/time/time.h"
 #include "components/history/core/browser/history_service.h"
@@ -378,13 +378,15 @@ class ContentSuggestionsService : public KeyedService,
 
   // Observer for the IdentityManager. All observers are notified when the
   // signin state changes so that they can refresh their list of suggestions.
-  ScopedObserver<signin::IdentityManager, signin::IdentityManager::Observer>
-      identity_manager_observer_;
+  base::ScopedObservation<signin::IdentityManager,
+                          signin::IdentityManager::Observer>
+      identity_manager_observation_{this};
 
   // Observer for the HistoryService. All providers are notified when history is
   // deleted.
-  ScopedObserver<history::HistoryService, history::HistoryServiceObserver>
-      history_service_observer_;
+  base::ScopedObservation<history::HistoryService,
+                          history::HistoryServiceObserver>
+      history_service_observation_{this};
 
   base::ObserverList<Observer>::Unchecked observers_;
 

components/ntp_snippets/reading_list/reading_list_suggestions_provider.cc

@@ -43,7 +43,7 @@ ReadingListSuggestionsProvider::ReadingListSuggestionsProvider(
 
   // If the ReadingListModel is loaded, this will trigger a call to
   // ReadingListModelLoaded. Keep it as last instruction.
-  scoped_observer_.Add(reading_list_model_);
+  scoped_observation_.Observe(reading_list_model_);
 }
 
 ReadingListSuggestionsProvider::~ReadingListSuggestionsProvider() {}
@@ -160,7 +160,8 @@ void ReadingListSuggestionsProvider::ReadingListModelLoaded(
 void ReadingListSuggestionsProvider::ReadingListModelBeingDeleted(
     const ReadingListModel* model) {
   DCHECK(model == reading_list_model_);
-  scoped_observer_.Remove(reading_list_model_);
+  DCHECK(scoped_observation_.IsObservingSource(reading_list_model_));
+  scoped_observation_.RemoveObservation();
   reading_list_model_ = nullptr;
 }
 

components/ntp_snippets/reading_list/reading_list_suggestions_provider.h

@@ -8,7 +8,7 @@
 #include <set>
 #include <string>
 
-#include "base/scoped_observer.h"
+#include "base/scoped_observation.h"
 #include "components/ntp_snippets/callbacks.h"
 #include "components/ntp_snippets/category.h"
 #include "components/ntp_snippets/category_info.h"
@@ -74,8 +74,8 @@ class ReadingListSuggestionsProvider : public ContentSuggestionsProvider,
   const Category provided_category_;
 
   ReadingListModel* reading_list_model_;
-  ScopedObserver<ReadingListModel, ReadingListModelObserver> scoped_observer_{
-      this};
+  base::ScopedObservation<ReadingListModel, ReadingListModelObserver>
+      scoped_observation_{this};
 
   DISALLOW_COPY_AND_ASSIGN(ReadingListSuggestionsProvider);
 };

components/ntp_snippets/remote/remote_suggestions_status_service.h

@@ -6,7 +6,7 @@
 #define COMPONENTS_NTP_SNIPPETS_REMOTE_REMOTE_SUGGESTIONS_STATUS_SERVICE_H_
 
 #include "base/callback.h"
-#include "base/scoped_observer.h"
+#include "base/scoped_observation.h"
 #include "components/prefs/pref_change_registrar.h"
 
 namespace ntp_snippets {

components/ntp_snippets/remote/remote_suggestions_status_service_impl.h

@@ -6,7 +6,7 @@
 #define COMPONENTS_NTP_SNIPPETS_REMOTE_REMOTE_SUGGESTIONS_STATUS_SERVICE_IMPL_H_
 
 #include "base/callback.h"
-#include "base/scoped_observer.h"
+#include "base/scoped_observation.h"
 #include "components/ntp_snippets/remote/remote_suggestions_status_service.h"
 #include "components/prefs/pref_change_registrar.h"