Add ContentSuggestionsMediator

ios/chrome/browser/content_suggestions/content_suggestions_service_bridge_observer.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_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_SERVICE_BRIDGE_OBSERVER_H_
+#define IOS_CHROME_BROWSER_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_SERVICE_BRIDGE_OBSERVER_H_
+
+#include "components/ntp_snippets/content_suggestions_service.h"
+
+// Protocol duplicating all ContentSuggestionsService Observer methods in
+// Objective-C.
+@protocol ContentSuggestionsServiceBridgeObserver
+
+- (void)onNewSuggestions:(ntp_snippets::Category)category;
+- (void)onCategory:(ntp_snippets::Category)category
+     statusChanged:(ntp_snippets::CategoryStatus)status;
+- (void)onSuggestionInvalidated:
+    (const ntp_snippets::ContentSuggestion::ID&)suggestion_id;
+- (void)onFullRefreshRequired;
+- (void)contentSuggestionsServiceShutdown;
+
+@end
+
+// Observer for the ContentSuggestionsService that translates all the callbacks
+// to Objective-C calls.
+class ContentSuggestionsServiceBridge
+    : public ntp_snippets::ContentSuggestionsService::Observer {
+ public:
+  ContentSuggestionsServiceBridge(
+      id<ContentSuggestionsServiceBridgeObserver> observer,
+      ntp_snippets::ContentSuggestionsService* service);
+  ~ContentSuggestionsServiceBridge() override;
+
+ private:
+  void OnNewSuggestions(ntp_snippets::Category category) override;
+  void OnCategoryStatusChanged(
+      ntp_snippets::Category category,
+      ntp_snippets::CategoryStatus new_status) override;
+  void OnSuggestionInvalidated(
+      const ntp_snippets::ContentSuggestion::ID& suggestion_id) override;
+  void OnFullRefreshRequired() override;
+  void ContentSuggestionsServiceShutdown() override;
+
+  __unsafe_unretained id<ContentSuggestionsServiceBridgeObserver> observer_;
+  ntp_snippets::ContentSuggestionsService* service_;  // weak
+
+  DISALLOW_COPY_AND_ASSIGN(ContentSuggestionsServiceBridge);
+};
+
+#endif  // IOS_CHROME_BROWSER_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_SERVICE_BRIDGE_OBSERVER_H_