Retire ScopedObserver in /components/history/core/browser/sync.

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=tschumann@chromium.org

Bug: 1145565
Change-Id: Iecd38a26630d7a6565455c42942b4b61144f1d2f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2532719
Auto-Submit: Sigurður Ásgeirsson <siggi@chromium.org>
Reviewed-by: Tim Schumann <tschumann@chromium.org>
Commit-Queue: Tim Schumann <tschumann@chromium.org>
Cr-Commit-Position: refs/heads/master@{#826716}

components/history/core/browser/sync/typed_url_sync_bridge.cc

@@ -436,7 +436,7 @@ void TypedURLSyncBridge::OnURLsDeleted(HistoryBackend* history_backend,
 void TypedURLSyncBridge::Init() {
   DCHECK(sequence_checker_.CalledOnValidSequence());
 
-  history_backend_observer_.Add(history_backend_);
+  history_backend_observation_.Observe(history_backend_);
   LoadMetadata();
 }
 

components/history/core/browser/sync/typed_url_sync_bridge.h

@@ -12,7 +12,7 @@
 #include <utility>
 #include <vector>
 
-#include "base/scoped_observer.h"
+#include "base/scoped_observation.h"
 #include "components/history/core/browser/history_backend.h"
 #include "components/history/core/browser/history_backend_observer.h"
 #include "components/history/core/browser/sync/typed_url_sync_metadata_database.h"
@@ -247,8 +247,8 @@ class TypedURLSyncBridge : public syncer::ModelTypeSyncBridge,
 
   // Tracks observed history backend, for receiving updates from history
   // backend.
-  ScopedObserver<HistoryBackend, HistoryBackendObserver>
-      history_backend_observer_{this};
+  base::ScopedObservation<HistoryBackend, HistoryBackendObserver>
+      history_backend_observation_{this};
 
   DISALLOW_COPY_AND_ASSIGN(TypedURLSyncBridge);
 };

components/history/core/browser/sync/typed_url_sync_bridge_unittest.cc

@@ -313,7 +313,8 @@ class TypedURLSyncBridgeTest : public testing::Test {
             mock_processor_.CreateForwardingProcessor());
     typed_url_sync_bridge_ = bridge.get();
     typed_url_sync_bridge_->Init();
-    typed_url_sync_bridge_->history_backend_observer_.RemoveAll();
+    if (typed_url_sync_bridge_->history_backend_observation_.IsObserving())
+      typed_url_sync_bridge_->history_backend_observation_.RemoveObservation();
     fake_history_backend_->SetTypedURLSyncBridgeForTest(std::move(bridge));
   }
 
@@ -408,10 +409,12 @@ class TypedURLSyncBridgeTest : public testing::Test {
   }
 
   void AddObserver() {
-    bridge()->history_backend_observer_.Add(fake_history_backend_.get());
+    bridge()->history_backend_observation_.Observe(fake_history_backend_.get());
   }
 
-  void RemoveObserver() { bridge()->history_backend_observer_.RemoveAll(); }
+  void RemoveObserver() {
+    bridge()->history_backend_observation_.RemoveObservation();
+  }
 
   // Fills |specifics| with the sync data for |url| and |visits|.
   static bool WriteToTypedUrlSpecifics(const URLRow& url,