Move the ReadingListModel in a Mediator

ios/chrome/browser/ui/reading_list/reading_list_data_sink.h

Index: ios/chrome/browser/ui/reading_list/reading_list_data_sink.h
diff --git a/ios/chrome/browser/ui/reading_list/reading_list_data_sink.h b/ios/chrome/browser/ui/reading_list/reading_list_data_sink.h
new file mode 100644
index 0000000000000000000000000000000000000000..87eae5d7e4e2a77fb2aa8a669019d03046917ed6
--- /dev/null
+++ b/ios/chrome/browser/ui/reading_list/reading_list_data_sink.h
@@ -0,0 +1,23 @@
+// 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_UI_READING_LIST_READING_LIST_DATA_SINK_H_
+#define IOS_CHROME_BROWSER_UI_READING_LIST_READING_LIST_DATA_SINK_H_
+
+@protocol ReadingListDataSource;
+
+// Data Sink for the Reading List UI, receiving informations from the data
+// source.
+@protocol ReadingListDataSink
+
+// Called by the data source when it is ready.
+- (void)dataSourceReady:(id<ReadingListDataSource>)dataSource;
+
+// TODO(crbug.com/721758): Group and rename those two methods.
+- (void)readingListModelDidApplyChanges;
+- (void)readingListModelCompletedBatchUpdates;
+
+@end
+
+#endif  // IOS_CHROME_BROWSER_UI_READING_LIST_READING_LIST_DATA_SINK_H_