Create an Obj-C bridge for MostVisitedSitesObserver

ios/chrome/browser/ntp_tiles/most_visited_sites_observer_bridge.h

+// Copyright 2017 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_NTP_TILES_MOST_VISITED_SITES_OBSERVER_BRIDGE_H_
+#define IOS_CHROME_BROWSER_NTP_TILES_MOST_VISITED_SITES_OBSERVER_BRIDGE_H_
+
+#import <Foundation/Foundation.h>
+
+#include "base/ios/weak_nsobject.h"
+#include "components/ntp_tiles/most_visited_sites.h"
+
+// Observes MostVisitedSites events from Objective-C. To use as a
+// ntp_tiles::MostVisitedSites::Observer, wrap in a
+// MostVisitedSitesObserverBridge.
+@protocol MostVisitedSitesObserving<NSObject>
+
+// Invoked by ntp_tiles::MostVisitedSites::Observer::OnMostVisitedURLsAvailable.
+- (void)onMostVisitedURLsAvailable:
+    (const ntp_tiles::NTPTilesVector&)mostVisited;
+
+// Invoked by ntp_tiles::MostVisitedSites::Observer::OnIconMadeAvailable.
+- (void)onIconMadeAvailable:(const GURL&)siteURL;
+
+@end
+
+namespace ntp_tiles {
+
+// Observer for the MostVisitedSites that translates all the callbacks to
+// Objective-C calls.
+class MostVisitedSitesObserverBridge : public MostVisitedSites::Observer {
+ public:
+  MostVisitedSitesObserverBridge(id<MostVisitedSitesObserving> observer);
+  ~MostVisitedSitesObserverBridge() override;
+
+  void OnMostVisitedURLsAvailable(const NTPTilesVector& most_visited) override;
+  void OnIconMadeAvailable(const GURL& site_url) override;
+
+ private:
+  base::WeakNSProtocol<id<MostVisitedSitesObserving>> observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(MostVisitedSitesObserverBridge);
+};
+
+}  // namespace ntp_tiles
+
+#endif  // IOS_CHROME_BROWSER_NTP_TILES_MOST_VISITED_SITES_OBSERVER_BRIDGE_H_