Refactor image_path to use asset_path directly

actionpack/lib/sprockets/helpers/rails_helper.rb

@@ -61,7 +61,7 @@ def asset_path(source, options = {})
       end
 
       def image_path(source)
-        asset_paths.compute_public_path(source, asset_prefix)
+        asset_path(source)
       end
       alias_method :path_to_image, :image_path # aliased to avoid conflicts with an image_path named route