removes code written for Ruby < 1.8.7

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

@@ -49,13 +49,6 @@ def mb_chars
     def is_utf8?
       ActiveSupport::Multibyte::Chars.consumes?(self)
     end
-
-    unless '1.8.7 and later'.respond_to?(:chars)
-      def chars
-        ActiveSupport::Deprecation.warn('String#chars has been deprecated in favor of String#mb_chars.', caller)
-        mb_chars
-      end
-    end
   else
     def mb_chars #:nodoc
       self

activesupport/test/core_ext/string_ext_test.rb

@@ -230,18 +230,6 @@ def test_string_should_recognize_utf8_strings
     assert !BYTE_STRING.is_utf8?
   end
 
-  if RUBY_VERSION < '1.8.7'
-    def test_core_ext_adds_chars
-      assert UNICODE_STRING.respond_to?(:chars)
-    end
-
-    def test_chars_warns_about_deprecation
-      assert_deprecated("String#chars") do
-        ''.chars
-      end
-    end
-  end
-
   if RUBY_VERSION < '1.9'
     def test_mb_chars_returns_self_when_kcode_not_set
       with_kcode('none') do