Add ContentSuggestionsMediator

ios/chrome/browser/ui/content_suggestions/content_suggestions_data_sink.h

Index: ios/chrome/browser/ui/content_suggestions/content_suggestions_data_sink.h
diff --git a/ios/chrome/browser/ui/content_suggestions/content_suggestions_data_sink.h b/ios/chrome/browser/ui/content_suggestions/content_suggestions_data_sink.h
new file mode 100644
index 0000000000000000000000000000000000000000..fc6aa3598375c26cd5c3df63038e1cba8fb93815
--- /dev/null
+++ b/ios/chrome/browser/ui/content_suggestions/content_suggestions_data_sink.h
@@ -0,0 +1,17 @@
+// 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_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_DATA_SINK_H_
+#define IOS_CHROME_BROWSER_UI_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_DATA_SINK_H_
+
+// Data sink for the ContentSuggestions. It will be notified when new data need
+// to be pulled.
+@protocol ContentSuggestionsDataSink
+
+// Notifies the Data Sink that new data are available.

[marq (ping after 24h), 2017/01/27 12:44:55]

Super nit: 'data' is the plural of the singular 'datum', but it is usually
treated like a grammatically singular mass noun (like 'water', 'dust', 'food').
So: 'new data is available'.

[gambard, 2017/01/30 15:19:17]

Oh. Ok, I always treated it as plural.

+- (void)dataAvailable;

[marq (ping after 24h), 2017/01/27 12:44:55]

This is interesting to consider and I don't have any concrete answers yet -- but
should this protocol push the data, or just alert the sink and let it pull via
the DataSource protocol? No change needed, but something to consider as this
evolves.

[gambard, 2017/01/30 15:19:17]

By your own documentation: "The dataSource pattern is pull, not push." :)
I will see how it evolves.

+
+@end
+
+#endif  // IOS_CHROME_BROWSER_UI_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_DATA_SINK_H_