This was generated with: ./mach cargo fmt --package selectors && ./mach cargo fmt --package servo_arc && ./mach cargo fmt --package style Using rustfmt 0.4.1-nightly (a4462d1 2018-03-26)
This more concrete wrapper type can write a prefix the very first time something is written to it. This allows removing plenty of useless monomorphisations caused by the former W/SequenceWriter<W> pair of types.
