Don't generate strings to log unless they'll actually get logged.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@7757 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/lib/action_controller/base.rb

@@ -1097,7 +1097,7 @@ module ActionController #:nodoc:
       end
 
       def log_processing
-        if logger
+        if logger && logger.info?
           logger.info "\n\nProcessing #{controller_class_name}\##{action_name} (for #{request_origin}) [#{request.method.to_s.upcase}]"
           logger.info "  Session ID: #{@_session.session_id}" if @_session and @_session.respond_to?(:session_id)
           logger.info "  Parameters: #{respond_to?(:filter_parameters) ? filter_parameters(params).inspect : params.inspect}"