[ios] Adds DiscoverFeedVC as ContentSuggestions ChildVC

In order to properly handle the life cycle of the DiscoverFeedVC the
following changes are made:

- Makes the DiscoverVC a ChildVC of the ContentSuggestionsVC and removes
it on dealloc.
- ContentSuggestionsCoordinator now owns the DiscoverFeedVC.
- Adds isDiscoverItem method in ContentSuggestionsCollectionUpdater.

Without these changes the DiscoverFeedVC is not properly dealloc-ed
and might lead to some crashes.

Bug: 1085419
Change-Id: If4b7c1e2ada6876c036527ac5eefdae020339327
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2258367
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#781415}

ios/chrome/browser/ui/content_suggestions/cells/content_suggestions_discover_item.h

@@ -19,7 +19,7 @@
     : CollectionViewItem <SuggestedContent>
 
 // Contains the Discover feed coming from Discover provider.
-@property(strong, nonatomic) UIViewController* discoverFeed;
+@property(nonatomic, weak) UIViewController* discoverFeed;
 
 @end
 

ios/chrome/browser/ui/content_suggestions/cells/content_suggestions_discover_item.mm

@@ -13,7 +13,7 @@
 @interface ContentSuggestionsDiscoverItem ()
 
 // Contains a reference to the last configured cell containing the feed.
-@property(strong, nonatomic) ContentSuggestionsDiscoverCell* lastConfiguredCell;
+@property(nonatomic, weak) ContentSuggestionsDiscoverCell* lastConfiguredCell;
 
 @end
 
@@ -46,7 +46,7 @@
 @interface ContentSuggestionsDiscoverCell ()
 
 // The Discover feed which acts as the cell's content.
-@property(strong, nonatomic) UIViewController* discoverFeed;
+@property(nonatomic, weak) UIViewController* discoverFeed;
 
 @end
 

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

@@ -84,6 +84,9 @@ addSuggestionsToModel:
 // items.
 - (BOOL)isContentSuggestionsSection:(NSInteger)section;
 
+// Returns whether |itemType| is a Discover ItemType.
+- (BOOL)isDiscoverItem:(NSInteger)itemType;
+
 // Dismisses the |item| from the model. Does not change the UI.
 - (void)dismissItem:(CollectionViewItem<SuggestedContent>*)item;
 

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

@@ -580,6 +580,10 @@ addSuggestionsToModel:(NSArray<CSCollectionViewItem*>*)suggestions
           sectionIdentifierForSection:section]);
 }
 
+- (BOOL)isDiscoverItem:(NSInteger)itemType {
+  return itemType == ItemTypeDiscover;
+}
+
 - (void)dismissItem:(CSCollectionViewItem*)item {
   [self.dataSource dismissSuggestion:item.suggestionIdentifier];
 }

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

@@ -69,6 +69,7 @@
     ContentSuggestionsHeaderSynchronizer* headerCollectionInteractionHandler;
 @property(nonatomic, strong) ContentSuggestionsMetricsRecorder* metricsRecorder;
 @property(nonatomic, strong) NTPHomeMediator* NTPMediator;
+@property(nonatomic, strong) UIViewController* discoverFeedViewController;
 
 // Redefined as readwrite.
 @property(nonatomic, strong, readwrite)
@@ -156,7 +157,7 @@
       ReadingListModelFactory::GetForBrowserState(
           self.browser->GetBrowserState());
 
-  UIViewController* discoverFeed =
+  self.discoverFeedViewController =
       ios::GetChromeBrowserProvider()
           ->GetDiscoverFeedProvider()
           ->NewFeedViewController(static_cast<id<ApplicationCommands>>(
@@ -169,7 +170,7 @@
              mostVisitedSite:std::move(mostVisitedFactory)
             readingListModel:readingListModel
                  prefService:prefs
-                discoverFeed:discoverFeed];
+                discoverFeed:self.discoverFeedViewController];
   self.contentSuggestionsMediator.commandHandler = self.NTPMediator;
   self.contentSuggestionsMediator.headerProvider = self.headerController;
   self.contentSuggestionsMediator.contentArticlesExpanded =

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

@@ -11,6 +11,7 @@
 #import "ios/chrome/browser/ui/collection_view/cells/collection_view_item.h"
 #import "ios/chrome/browser/ui/collection_view/collection_view_model.h"
 #import "ios/chrome/browser/ui/content_suggestions/cells/content_suggestions_cell.h"
+#import "ios/chrome/browser/ui/content_suggestions/cells/content_suggestions_discover_item.h"
 #import "ios/chrome/browser/ui/content_suggestions/cells/content_suggestions_most_visited_cell.h"
 #import "ios/chrome/browser/ui/content_suggestions/cells/suggested_content.h"
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_collection_updater.h"
@@ -56,6 +57,10 @@ NSString* const kContentSuggestionsMostVisitedAccessibilityIdentifierPrefix =
 // The overscroll actions controller managing accelerators over the toolbar.
 @property(nonatomic, strong)
     OverscrollActionsController* overscrollActionsController;
+
+// The DiscoverFeedVC that might be displayed by this VC.
+@property(nonatomic, weak) UIViewController* discoverFeedVC;
+
 @end
 
 @implementation ContentSuggestionsViewController
@@ -83,6 +88,9 @@ NSString* const kContentSuggestionsMostVisitedAccessibilityIdentifierPrefix =
 }
 
 - (void)dealloc {
+  [self.discoverFeedVC willMoveToParentViewController:nil];
+  [self.discoverFeedVC.view removeFromSuperview];
+  [self.discoverFeedVC removeFromParentViewController];
   [self.overscrollActionsController invalidate];
 }
 
@@ -366,6 +374,19 @@ NSString* const kContentSuggestionsMostVisitedAccessibilityIdentifierPrefix =
   CSCollectionViewItem* item =
       [self.collectionViewModel itemAtIndexPath:indexPath];
 
+  if ([self.collectionUpdater
+          isDiscoverItem:[self.collectionViewModel
+                             itemTypeForIndexPath:indexPath]]) {
+    ContentSuggestionsDiscoverItem* discoverFeedItem =
+        static_cast<ContentSuggestionsDiscoverItem*>(item);
+    self.discoverFeedVC = discoverFeedItem.discoverFeed;
+    [self addChildViewController:self.discoverFeedVC];
+    UICollectionViewCell* cell = [super collectionView:collectionView
+                                cellForItemAtIndexPath:indexPath];
+    [self.discoverFeedVC didMoveToParentViewController:self];
+    return cell;
+  }
+
   if ([self.collectionUpdater isContentSuggestionsSection:indexPath.section] &&
       [self.collectionUpdater contentSuggestionTypeForItem:item] !=
           ContentSuggestionTypeEmpty &&