Fix animation on ContentSuggestions rotations

When there is an animation on the NTP screen with ContentSuggestions,
the appearing and disappearing icons are shown with an alpha of 1
during the whole animation.
This CL fixes this by reloading the data during the rotation.

Before: https://drive.google.com/open?id=0B21N-0pPGAuJMHVhWDRvdU55ODg
After: https://drive.google.com/open?id=0B21N-0pPGAuJYm13cW5IVDRiUjQ

BUG=700375

Change-Id: Ie2c928ff1d012439cf329948713f2ff46887b7d2
Reviewed-on: https://chromium-review.googlesource.com/561776
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Louis Romero <lpromero@chromium.org>
Cr-Commit-Position: refs/heads/master@{#485199}

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

@@ -76,7 +76,8 @@ addSuggestionsToModel:
 // header containing the fake omnibox and the logo.
 - (BOOL)isHeaderSection:(NSInteger)section;
 
-// Updates the number of Most Visited tiles shown for the |size|.
+// Updates the number of Most Visited tiles shown for the |size| on the model
+// only. The collection needs to be updated separately.
 - (void)updateMostVisitedForSize:(CGSize)size;
 
 // Dismisses the |item| from the model. Does not change the UI.

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

@@ -446,24 +446,22 @@ addSuggestionsToModel:(NSArray<CSCollectionViewItem*>*)suggestions
   if (currentCount == newCount)
     return;
 
-  // If the animations are enabled, the items are added then the rotation
-  // animation is triggered, creating a weird sequenced animation.
-  [UIView setAnimationsEnabled:NO];
   if (currentCount > newCount) {
     for (NSInteger i = newCount; i < currentCount; i++) {
-      NSIndexPath* itemToRemove =
-          [NSIndexPath indexPathForItem:newCount inSection:mostVisitedSection];
-      [self.collectionViewController dismissEntryAtIndexPath:itemToRemove];
+      [self.collectionViewController.collectionViewModel
+                 removeItemWithType:ItemTypeMostVisited
+          fromSectionWithIdentifier:SectionIdentifierMostVisited
+                            atIndex:newCount];
     }
   } else {
-    NSMutableArray* itemsToBeAdded = [NSMutableArray array];
     for (NSInteger i = currentCount; i < newCount; i++) {
-      [itemsToBeAdded addObject:mostVisited[i]];
+      CSCollectionViewItem* item = mostVisited[i];
+      item.type = ItemTypeMostVisited;
+      [self.collectionViewController.collectionViewModel
+                          addItem:item
+          toSectionWithIdentifier:SectionIdentifierMostVisited];
     }
-    [self.collectionViewController addSuggestions:itemsToBeAdded
-                                    toSectionInfo:mostVisitedSectionInfo];
   }
-  [UIView setAnimationsEnabled:YES];
 }
 
 - (void)dismissItem:(CSCollectionViewItem*)item {

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

@@ -204,7 +204,7 @@ BOOL ShouldCellsBeFullWidth(UITraitCollection* collection) {
         UIEdgeInsetsMake(0, self.cardStyleMargin, 0, self.cardStyleMargin);
   }
   [self.collectionUpdater updateMostVisitedForSize:size];
-  [self.collectionView.collectionViewLayout invalidateLayout];
+  [self.collectionView reloadData];
 }
 
 - (void)willTransitionToTraitCollection:(UITraitCollection*)newCollection
@@ -212,6 +212,10 @@ BOOL ShouldCellsBeFullWidth(UITraitCollection* collection) {
                   (id<UIViewControllerTransitionCoordinator>)coordinator {
   [super willTransitionToTraitCollection:newCollection
                withTransitionCoordinator:coordinator];
+  // Invalidating the layout after changing the cellStyle/contentInset results
+  // in the layout not being updated. Do it before to have it taken into
+  // account.
+  [self.collectionView.collectionViewLayout invalidateLayout];
   if (ShouldCellsBeFullWidth(newCollection)) {
     self.collectionView.contentInset = UIEdgeInsetsZero;
     self.styler.cellStyle = MDCCollectionViewCellStyleGrouped;
@@ -220,7 +224,6 @@ BOOL ShouldCellsBeFullWidth(UITraitCollection* collection) {
         UIEdgeInsetsMake(0, self.cardStyleMargin, 0, self.cardStyleMargin);
     self.styler.cellStyle = MDCCollectionViewCellStyleCard;
   }
-  [self.collectionView.collectionViewLayout invalidateLayout];
 }
 
 #pragma mark - UICollectionViewDelegate