Adds a new constructor for gfx::Image on iOS.

ios/chrome/browser/suggestions/ios_image_decoder_impl.mm

Index: ios/chrome/browser/suggestions/ios_image_decoder_impl.mm
diff --git a/ios/chrome/browser/suggestions/ios_image_decoder_impl.mm b/ios/chrome/browser/suggestions/ios_image_decoder_impl.mm
index 52fc55073344bc9ee36b61d96cc025bec5caf310..5e87fcc984cc07038842d421182cad71d0870c61 100644
--- a/ios/chrome/browser/suggestions/ios_image_decoder_impl.mm
+++ b/ios/chrome/browser/suggestions/ios_image_decoder_impl.mm
@@ -148,7 +148,7 @@ void IOSImageDecoderImpl::CreateUIImageAndRunCallback(
       // This constructor does not retain the image, but expects to take the
       // ownership, therefore, |ui_image| is retained here, but not released
       // afterwards.
-      gfx::Image gfx_image([ui_image retain]);
+      gfx::Image gfx_image(ui_image, base::scoped_policy::RETAIN);
       callback.Run(gfx_image);
       return;
     }