[iOS] Fix Articles Context Menu With Native CtxMenu Flag On

With the flag on, articles context menus weren't working. Moving the
flag check to the MostVisited flow instead of overall the long-press
gesture recognizer fixes it.

Bug: 1115970
Change-Id: Ic9945928c949cbef9ed874d5a381b071b18a54d3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2354272
Auto-Submit: Sebastien Lalancette <seblalancette@chromium.org>
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797786}

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

@@ -254,14 +254,12 @@ NSString* const kContentSuggestionsMostVisitedAccessibilityIdentifierPrefix =
   ApplyVisualConstraints(@[ @"V:|[collection]|", @"H:|[collection]|" ],
                          @{@"collection" : self.collectionView});
 
-  if (!IsNativeContextMenuEnabled()) {
     UILongPressGestureRecognizer* longPressRecognizer =
         [[UILongPressGestureRecognizer alloc]
             initWithTarget:self
                     action:@selector(handleLongPress:)];
     longPressRecognizer.delegate = self;
     [self.collectionView addGestureRecognizer:longPressRecognizer];
-  }
 
   self.overscrollActionsController = [[OverscrollActionsController alloc]
       initWithScrollView:self.collectionView];
@@ -830,10 +828,12 @@ NSString* const kContentSuggestionsMostVisitedAccessibilityIdentifierPrefix =
                           readLaterAction:NO];
       break;
     case ContentSuggestionTypeMostVisited:
-      [self.suggestionCommandHandler
-          displayContextMenuForMostVisitedItem:touchedItem
-                                       atPoint:touchLocation
-                                   atIndexPath:touchedItemIndexPath];
+      if (!IsNativeContextMenuEnabled()) {
+        [self.suggestionCommandHandler
+            displayContextMenuForMostVisitedItem:touchedItem
+                                         atPoint:touchLocation
+                                     atIndexPath:touchedItemIndexPath];
+      }
       break;
     default:
       break;