Pass UIImage instead of gfx::Image in ContentSuggestions

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

 // 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.
 
 #ifndef IOS_CHROME_BROWSER_UI_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_IMAGE_UPDATER_H_
 #define IOS_CHROME_BROWSER_UI_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_IMAGE_UPDATER_H_
 
-#import <Foundation/Foundation.h>
-
-namespace gfx {
-class Image;
-}
+#import <UIKit/UIKit.h>
 
 @class ContentSuggestionIdentifier;
 
 // Protocol for an object able to fetch the image associated with a suggestion.
 @protocol ContentSuggestionsImageFetcher
 
 // Fetches the image associated with the |suggestionIdentifier| and passes it to
-// the |callback|.
+// the |callback|. The callback may never be called.
 - (void)fetchImageForSuggestion:
             (ContentSuggestionIdentifier*)suggestionIdentifier
-                       callback:(void (^)(const gfx::Image&))callback;
+                       callback:(void (^)(UIImage*))callback;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_IMAGE_UPDATER_H_