Get Suggestions image only if it is not empty

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

 // Copyright 2017 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/chrome/browser/ui/content_suggestions/content_suggestions_article_item.h"
 
 #include "base/time/time.h"
 #import "ios/chrome/browser/ui/uikit_ui_util.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 namespace {
 const CGFloat kImageSize = 100;
 const CGFloat kStandardSpacing = 8;
 }
 
 @interface ContentSuggestionsArticleItem ()
 
 @property(nonatomic, copy) NSString* subtitle;
-@property(nonatomic, weak) id<ContentSuggestionsArticleItemDelegate> delegate;
+// Used to check if the image has already been fetched. There is no way to
+// discriminate between failed image download and nonexitent image. The article
+// tries to download the image only once.
+@property(nonatomic, assign) BOOL imageFetched;
 
 @end
 
 #pragma mark - ContentSuggestionsArticleItem
 
 @implementation ContentSuggestionsArticleItem
 
 @synthesize title = _title;
 @synthesize subtitle = _subtitle;
 @synthesize image = _image;
 @synthesize articleURL = _articleURL;
 @synthesize publisher = _publisher;
 @synthesize publishDate = _publishDate;
 @synthesize suggestionIdentifier = _suggestionIdentifier;
 @synthesize delegate = _delegate;
-@synthesize imageBeingFetched = _imageBeingFetched;
+@synthesize imageFetched = _imageFetched;
 
 - (instancetype)initWithType:(NSInteger)type
                        title:(NSString*)title
                     subtitle:(NSString*)subtitle
                     delegate:(id<ContentSuggestionsArticleItemDelegate>)delegate
                          url:(const GURL&)url {
   self = [super initWithType:type];
   if (self) {
     self.cellClass = [ContentSuggestionsArticleCell class];
     _title = [title copy];
     _subtitle = [subtitle copy];
     _articleURL = url;
     _delegate = delegate;
   }
   return self;
 }
 
 - (void)configureCell:(ContentSuggestionsArticleCell*)cell {
   [super configureCell:cell];
-  if (!self.image && !self.imageBeingFetched) {
+  if (!self.image && !self.imageFetched) {
+    self.imageFetched = YES;
+    // Fetch the image. During the fetch the cell's image should still be set to
+    // nil.
     [self.delegate loadImageForArticleItem:self];
   }
   cell.titleLabel.text = _title;
   cell.subtitleLabel.text = _subtitle;
   cell.imageView.image = _image;
   [cell setPublisherName:self.publisher date:self.publishDate];
 }
 
 @end
 
@@ skipping 91 matching lines @@
   CGFloat parentWidth = CGRectGetWidth(self.contentView.bounds);
   self.subtitleLabel.preferredMaxLayoutWidth =
       parentWidth - self.imageView.bounds.size.width - 3 * 8;
 
   // Re-layout with the new preferred width to allow the label to adjust its
   // height.
   [super layoutSubviews];
 }
 
 @end