sources: fix sources sometimes choosing wrong strategy (fix #3968)

Fix sources choosing the wrong strategy when the referer belongs to a
different site (for example, when uploading a twitter post with a pixiv
referer).

* Fix `match?` to only consider the main url, not the referer.

* Change `match?` to match against a list of domains given by the `domains` method.

* Change `match?` to an instance method.

app/logical/sources/strategies/deviant_art.rb

@@ -49,8 +49,8 @@ module Sources
       PATH_PROFILE = %r{\Ahttps?://(www\.)?deviantart\.com/#{ARTIST}/?\z}i
       SUBDOMAIN_PROFILE = %r{\Ahttps?://#{ARTIST}\.deviantart\.com/?\z}i
 
-      def self.match?(*urls)
-        urls.compact.any? { |x| x.match?(/^https?:\/\/(?:.+?\.)?deviantart\.(?:com|net)/) }
+      def domains
+        ["deviantart.net", "deviantart.com"]
       end
 
       def site_name