Extract String#bytesize shim

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

+unless '1.9'.respond_to?(:bytesize)
+  class String
+    alias :bytesize :size
+  end
+end

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

@@ -6,6 +6,7 @@
 =end
 
 if RUBY_VERSION < '1.9'
+  require 'active_support/core_ext/string/bytesize'
 
   # KeyError is raised by String#% when the string contains a named placeholder
   # that is not contained in the given arguments hash. Ruby 1.9 includes and
@@ -24,8 +25,6 @@ def initialize(message = nil)
   # the meaning of the msgids using "named argument" instead of %s/%d style.
 
   class String
-    # For older ruby versions, such as ruby-1.8.5
-    alias :bytesize :size unless instance_methods.find {|m| m.to_s == 'bytesize'}
     alias :interpolate_without_ruby_19_syntax :% # :nodoc:
 
     INTERPOLATION_PATTERN = Regexp.union(
@@ -90,4 +89,4 @@ def %(args)
       end
     end
   end
-end
+end
\ No newline at end of file

activesupport/test/core_ext/string_ext_test.rb

@@ -345,3 +345,10 @@ def test_string_interpolation_raises_an_argument_error_when_mixing_named_and_unn
     assert_raises(ArgumentError) { "%{name} %f" % [1.0, 2.0] }
   end
 end
+
+class StringBytesizeTest < Test::Unit::TestCase
+  def test_bytesize
+    assert_respond_to 'foo', :bytesize
+    assert_equal 3, 'foo'.bytesize
+  end
+end