Make content attributes optional

For normal images contentAttributes are optional in
the spec but the converter requires them. This makes
them optional.

Change-Id: I4073de51009e6e7802667b2d79a7ad485d939978
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2363477
Auto-Submit: Becca Hughes <beccahughes@chromium.org>
Commit-Queue: Sam Bowen <sgbowen@google.com>
Reviewed-by: Sam Bowen <sgbowen@google.com>
Cr-Commit-Position: refs/heads/master@{#799388}

chrome/browser/media/feeds/media_feeds_converter.cc

@@ -330,10 +330,7 @@ MediaFeedsConverter::GetMediaImage(const Property& property) {
     image->src = url->values->url_values[0];
 
     auto content_attributes = GetContentAttributes(image_object);
-    if (!content_attributes.has_value())
-      continue;
-
-    if (!content_attributes.value().empty()) {
+    if (content_attributes && !content_attributes.value().empty()) {
       image->content_attributes = std::move(content_attributes.value());
     }