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, 18 insertions, 0 deletions

diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md
index a2cf94fb42..82438cb766 100644
--- a/actionpack/CHANGELOG.md
+++ b/actionpack/CHANGELOG.md
@@ -1,5 +1,23 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   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>'
+
+    *Semyon Perepelitsa*
+
 *   Remove `BestStandardsSupport` middleware, !DOCTYPE html already triggers
     standards mode per http://msdn.microsoft.com/en-us/library/jj676915(v=vs.85).aspx
     and ChromeFrame header has been moved to `config.action_dispatch.default_headers`