Fix use of stringbuffer in pkg/args
Fix use of stringbuffer in pkg/args

Review URL: https://codereview.chromium.org//12335035

git-svn-id: 965eb99b257a0350f91a5ab8607b3dea57271703@18902 260f80e4-7a28-3924-810f-c04153c831b5

seaneagan/args,ronlobo/args,dart-lang/args,iansf/args