rollup merge of #21713: alexcrichton/second-pass-fmt

diff --cc src/libcollections/bit.rs
Simple merge

diff --cc src/libcollections/enum_set.rs
Simple merge

diff --cc src/libcollections/string.rs
Simple merge

diff --cc src/libcollections/vec.rs
Simple merge

diff --cc src/librustc/middle/infer/region_inference/graphviz.rs
Simple merge

diff --cc src/libserialize/json.rs
Simple merge