Avoid another CSS counters bug on IE7.

Closes sass#908

doc-src/SASS_CHANGELOG.md

@@ -14,6 +14,9 @@
 * Fixed a bug in the output of lists containing unary plus or minus
   operations during sass <=> scss conversion.
 
+* Avoid the [IE7 `content: counter` bug][cc bug] with `content: counters` as
+  well.
+
 ## 3.2.10
 
 * Use the Sass logger infrastructure for `@debug` directives.

lib/sass/script/functions.rb

@@ -1488,7 +1488,7 @@ def if(condition, if_true, if_false)
     end
     declare :if, [:condition, :if_true, :if_false]
 
-    # This function only exists as a workaround for IE7's [`content:counter`
+    # This function only exists as a workaround for IE7's [`content: counter`
     # bug][bug]. It works identically to any other plain-CSS function, except it
     # avoids adding spaces between the argument commas.
     #
@@ -1503,6 +1503,21 @@ def counter(*args)
     end
     declare :counter, [], :var_args => true
 
+    # This function only exists as a workaround for IE7's [`content: counters`
+    # bug][bug]. It works identically to any other plain-CSS function, except it
+    # avoids adding spaces between the argument commas.
+    #
+    # [bug]: http://jes.st/2013/ie7s-css-breaking-content-counter-bug/
+    #
+    # @example
+    #   counters(item, ".") => counters(item,".")
+    # @overload counters($args...)
+    # @return [String]
+    def counters(*args)
+      Sass::Script::String.new("counters(#{args.map {|a| a.to_s(options)}.join(',')})")
+    end
+    declare :counters, [], :var_args => true
+
     private
 
     # This method implements the pattern of transforming a numeric value into

test/sass/functions_test.rb

@@ -1046,6 +1046,12 @@ def test_counter
     assert_equal('counter(item,".")', evaluate('counter(item,".")'))
   end
 
+  def test_counters
+    assert_equal("counters(foo)", evaluate("counters(foo)"))
+    assert_equal('counters(item,".")', evaluate('counters(item, ".")'))
+    assert_equal('counters(item,".")', evaluate('counters(item,".")'))
+  end
+
   def test_keyword_args_rgb
     assert_equal(%Q{white}, evaluate("rgb($red: 255, $green: 255, $blue: 255)"))
   end