os: remove fstat TODO

R=rsc
CC=golang-dev
https://golang.org/cl/3559041

src/pkg/os/dir_darwin.go

@@ -10,7 +10,7 @@ import (
 )
 
 const (
-	blockSize = 4096 // TODO(r): use statfs
+	blockSize = 4096
 )
 
 // Readdirnames reads the contents of the directory associated with file and
@@ -23,7 +23,6 @@ func (file *File) Readdirnames(count int) (names []string, err Error) {
 	if file.dirinfo == nil {
 		file.dirinfo = new(dirInfo)
 		// The buffer must be at least a block long.
-		// TODO(r): use fstatfs to find fs block size.
 		file.dirinfo.buf = make([]byte, blockSize)
 	}
 	d := file.dirinfo

src/pkg/os/dir_freebsd.go

@@ -10,7 +10,7 @@ import (
 )
 
 const (
-	blockSize = 4096 // TODO(r): use statfs
+	blockSize = 4096
 )
 
 func (file *File) Readdirnames(count int) (names []string, err Error) {
@@ -18,7 +18,6 @@ func (file *File) Readdirnames(count int) (names []string, err Error) {
 	if file.dirinfo == nil {
 		file.dirinfo = new(dirInfo)
 		// The buffer must be at least a block long.
-		// TODO(r): use fstatfs to find fs block size.
 		file.dirinfo.buf = make([]byte, blockSize)
 	}
 	d := file.dirinfo

src/pkg/os/dir_linux.go

@@ -10,7 +10,7 @@ import (
 )
 
 const (
-	blockSize = 4096 // TODO(r): use statfs
+	blockSize = 4096
 )
 
 func clen(n []byte) int {
@@ -27,7 +27,6 @@ func (file *File) Readdirnames(count int) (names []string, err Error) {
 	if file.dirinfo == nil {
 		file.dirinfo = new(dirInfo)
 		// The buffer must be at least a block long.
-		// TODO(r): use fstatfs to find fs block size.
 		file.dirinfo.buf = make([]byte, blockSize)
 	}
 	d := file.dirinfo