Add support for HiDPI displays in gravatar service

app/services/gravatar_service.rb

 class GravatarService
   include Gitlab::CurrentSettings
 
-  def execute(email, size = nil)
+  def execute(email, size = nil, scale = 2)
     if current_application_settings.gravatar_enabled? && email.present?
       size = 40 if size.nil? || size <= 0
 
       sprintf gravatar_url,
         hash: Digest::MD5.hexdigest(email.strip.downcase),
-        size: size,
+        size: size * scale,
         email: email.strip
     end
   end

spec/helpers/application_helper_spec.rb

@@ -141,15 +141,19 @@ describe ApplicationHelper do
         stub_gravatar_setting(plain_url: 'http://example.local/?s=%{size}&hash=%{hash}')
 
         expect(gravatar_icon(user_email, 20)).
-          to eq('http://example.local/?s=20&hash=b58c6f14d292556214bd64909bcdb118')
+          to eq('http://example.local/?s=40&hash=b58c6f14d292556214bd64909bcdb118')
       end
 
       it 'accepts a custom size argument' do
-        expect(helper.gravatar_icon(user_email, 64)).to include '?s=64'
+        expect(helper.gravatar_icon(user_email, 64)).to include '?s=128'
       end
 
-      it 'defaults size to 40 when given an invalid size' do
-        expect(helper.gravatar_icon(user_email, nil)).to include '?s=40'
+      it 'defaults size to 40@2x when given an invalid size' do
+        expect(helper.gravatar_icon(user_email, nil)).to include '?s=80'
+      end
+
+      it 'accepts a scaling factor' do
+        expect(helper.gravatar_icon(user_email, 40, 3)).to include '?s=120'
       end
 
       it 'ignores case and surrounding whitespace' do