Add ContentSuggestionsMediator

ios/showcase/suggestions/sc_suggestions_coordinator.mm

 // Copyright 2016 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.
 
 #import "ios/showcase/suggestions/sc_suggestions_coordinator.h"
 
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_commands.h"
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_view_controller.h"
 #import "ios/showcase/common/protocol_alerter.h"
 
@@ skipping 16 matching lines @@
 @synthesize alerter = _alerter;
 
 #pragma mark - Coordinator
 
 - (void)start {
   self.alerter = [[ProtocolAlerter alloc]
       initWithProtocols:@[ @protocol(ContentSuggestionsCommands) ]];
   self.alerter.baseViewController = self.baseViewController;
 
   _suggestionViewController = [[ContentSuggestionsViewController alloc]
-      initWithStyle:CollectionViewControllerStyleDefault];
+      initWithStyle:CollectionViewControllerStyleDefault
+         dataSource:nil];
 
   _suggestionViewController.suggestionCommandHandler =
       reinterpret_cast<id<ContentSuggestionsCommands>>(self.alerter);
 
   [self.baseViewController pushViewController:_suggestionViewController
                                      animated:YES];
 }
 
 @end