Add ContentSuggestionsMediator

ios/chrome/browser/ui/content_suggestions/content_suggestions_collection_updater.mm

Index: ios/chrome/browser/ui/content_suggestions/content_suggestions_collection_updater.mm
diff --git a/ios/chrome/browser/ui/content_suggestions/content_suggestions_collection_updater.mm b/ios/chrome/browser/ui/content_suggestions/content_suggestions_collection_updater.mm
index 6ba3bf0d340c143416dae2fdfca4c943d48adf6a..a50816265429f9f597c407e4cc66ed6f8ad2db8d 100644
--- a/ios/chrome/browser/ui/content_suggestions/content_suggestions_collection_updater.mm
+++ b/ios/chrome/browser/ui/content_suggestions/content_suggestions_collection_updater.mm
@@ -9,6 +9,8 @@
 #import "ios/chrome/browser/ui/collection_view/collection_view_controller.h"
 #import "ios/chrome/browser/ui/collection_view/collection_view_model.h"
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_article_item.h"
+#import "ios/chrome/browser/ui/content_suggestions/content_suggestions_data_sink.h"
+#import "ios/chrome/browser/ui/content_suggestions/content_suggestions_data_source.h"
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_expandable_item.h"
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_favicon_item.h"
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_item.h"
@@ -19,9 +21,26 @@
 #error "This file requires ARC support."
 #endif
 
+@interface ContentSuggestionsCollectionUpdater ()<ContentSuggestionsDataSink>
+
+@property(nonatomic, strong) id<ContentSuggestionsDataSource> dataSource;

[lpromero, 2017/01/26 10:10:20]

Can we risk creating a cycle if the one creating and retaining the updater is
the data source? Worth mentioning in the header that this object has a strong
reference to the data source, so the caller should take action to break a
potential cycle when needed.

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

Does this need to be strong? Delegates usually aren't.

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

Yes, the data source should be kept alive by the coordinator.

+
+@end
+
 @implementation ContentSuggestionsCollectionUpdater
 
 @synthesize collectionViewController = _collectionViewController;
+@synthesize dataSource = _dataSource;
+
+- (instancetype)initWithDataSource:
+    (id<ContentSuggestionsDataSource>)dataSource {
+  self = [super init];
+  if (self) {
+    _dataSource = dataSource;
+    _dataSource.dataSink = self;
+  }
+  return self;
+}
 
 #pragma mark - Properties
 
@@ -30,6 +49,9 @@
   _collectionViewController = collectionViewController;
   [collectionViewController loadModel];
   CollectionViewModel* model = collectionViewController.collectionViewModel;
+
+  // Loads the data with the dataSource instead of hard coded value.

[lpromero, 2017/01/26 10:10:20]

Mark this with // PLACEHOLDER

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

Also, clarify that this is a change that needs to be made ("change this to load
the data ... ").

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

Done.

+
   NSInteger sectionIdentifier = kSectionIdentifierEnumZero;
 
   // Stack Item.
@@ -88,6 +110,13 @@
   }
 }
 
+#pragma mark - ContentSuggestionsDataSink
+
+- (void)dataAvailable {
+  [self.dataSource getMoreData];

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

Either delete the dataSource call or assign the result to something; the risk
here is that looks like it's causing the dataSource to do something, but the
current method definition returns an array. Better to code defensively even in
placeholder code.

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

Done.

+  // Do something.
+}
+
 #pragma mark - Public methods
 
 - (void)addTextItem:(NSString*)title