Fix `content_tag_for` with array html option.

It would embed array as string instead of joining it like `content_tag` does:

    content_tag(:td, class: ["foo", "bar"]){}
    #=> '<td class="foo bar"></td>'

Before:

    content_tag_for(:td, item, class: ["foo", "bar"]){}
    #=> '<td class="item [&quot;foo&quot;, &quot;bar&quot;]" id="item_1"></td>'

After:

    content_tag_for(:td, item, class: ["foo", "bar"]){}
    #=> '<td class="item foo bar" id="item_1"></td>'

1 files changed, 6 insertions, 0 deletions

diff --git a/actionpack/test/template/record_tag_helper_test.rb b/actionpack/test/template/record_tag_helper_test.rb
index 9c49438f6a..ab84bccb56 100644
--- a/actionpack/test/template/record_tag_helper_test.rb
+++ b/actionpack/test/template/record_tag_helper_test.rb
@@ -41,6 +41,12 @@ class RecordTagHelperTest < ActionView::TestCase
     assert_dom_equal expected, actual
   end
 
+  def test_content_tag_for_with_array_css_class
+    expected = %(<tr class="record_tag_post special odd" id="record_tag_post_45"></tr>)
+    actual = content_tag_for(:tr, @post, class: ["special", "odd"])
+    assert_dom_equal expected, actual
+  end
+
   def test_content_tag_for_with_prefix_and_extra_html_options
     expected = %(<tr class="archived_record_tag_post special" id="archived_record_tag_post_45" style='background-color: #f0f0f0'></tr>)
     actual = content_tag_for(:tr, @post, :archived, class: "special", style: "background-color: #f0f0f0")