drastically reduce object allocations

before this change, we were allocating AS::SafeBuffer objects that were
being interpolated in to a string, so the safe buffer object was being
thrown away.  This change only allocates a string (vs a string *and* a
safebuffer) and interpolates the string.

On my test application, this reduced the AS::SafeBuffer objects from
1527k per request to about 500 per request.

actionview/lib/action_view/helpers/tag_helper.rb

@@ -139,7 +139,7 @@ def escape_once(html)
 
         def content_tag_string(name, content, options, escape = true)
           tag_options = tag_options(options, escape) if options
-          content     = ERB::Util.h(content) if escape
+          content     = ERB::Util.unwrapped_html_escape(content) if escape
           "<#{name}#{tag_options}>#{PRE_CONTENT_STRINGS[name.to_sym]}#{content}</#{name}>".html_safe
         end
 
@@ -174,7 +174,7 @@ def boolean_tag_option(key)
 
         def tag_option(key, value, escape)
           value = value.join(" ") if value.is_a?(Array)
-          value = ERB::Util.h(value) if escape
+          value = ERB::Util.unwrapped_html_escape(value) if escape
           %(#{key}="#{value}")
         end
     end

activesupport/lib/active_support/core_ext/string/output_safety.rb

@@ -19,12 +19,7 @@ module Util
     #   puts html_escape('is a > 0 & a < 10?')
     #   # => is a &gt; 0 &amp; a &lt; 10?
     def html_escape(s)
-      s = s.to_s
-      if s.html_safe?
-        s
-      else
-        s.gsub(HTML_ESCAPE_REGEXP, HTML_ESCAPE).html_safe
-      end
+      unwrapped_html_escape(s).html_safe
     end
 
     # Aliasing twice issues a warning "discarding old...". Remove first to avoid it.
@@ -36,6 +31,18 @@ def html_escape(s)
     singleton_class.send(:remove_method, :html_escape)
     module_function :html_escape
 
+    # HTML escapes strings but doesn't wrap them with an ActiveSupport::SafeBuffer.
+    # This method is not for public consumption! Seriously!
+    def unwrapped_html_escape(s) # :nodoc:
+      s = s.to_s
+      if s.html_safe?
+        s
+      else
+        s.gsub(HTML_ESCAPE_REGEXP, HTML_ESCAPE)
+      end
+    end
+    module_function :unwrapped_html_escape
+
     # A utility method for escaping HTML without affecting existing escaped entities.
     #
     #   html_escape_once('1 < 2 &amp; 3')