[iOS] Upstream observer bridges

ios/chrome/browser/sync/sync_observer_bridge.h

+// Copyright 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef IOS_CHROME_BROWSER_SYNC_SYNC_OBSERVER_BRIDGE_H_
+#define IOS_CHROME_BROWSER_SYNC_SYNC_OBSERVER_BRIDGE_H_
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/ios/weak_nsobject.h"
+#include "base/scoped_observer.h"
+#include "components/sync_driver/sync_service_observer.h"
+
+namespace sync_driver {
+class SyncService;
+}
+
+@protocol SyncObserverModelBridge
+- (void)onSyncStateChanged;
+@end
+
+// C++ class to monitor profile sync status in Objective-C type.
+class SyncObserverBridge : public sync_driver::SyncServiceObserver {
+ public:
+  // |service| must outlive the SyncObserverBridge.
+  SyncObserverBridge(id<SyncObserverModelBridge> delegate,
+                     sync_driver::SyncService* service);
+
+  ~SyncObserverBridge() override;
+
+ private:
+   // sync_driver::SyncServiceObserver implementation:
+   void OnStateChanged() override;
+
+  base::WeakNSProtocol<id<SyncObserverModelBridge>> delegate_;
+  ScopedObserver<sync_driver::SyncService, sync_driver::SyncServiceObserver>
+      scoped_observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(SyncObserverBridge);
+};
+
+#endif  // IOS_CHROME_BROWSER_SYNC_SYNC_OBSERVER_BRIDGE_H_