Reorganize Multiprocess and implement for Windows

util/test/multiprocess_posix.cc

Index: util/test/multiprocess_posix.cc
diff --git a/util/test/multiprocess.cc b/util/test/multiprocess_posix.cc
similarity index 98%
rename from util/test/multiprocess.cc
rename to util/test/multiprocess_posix.cc
index c6b648b6abfa4dd833c2fdb99de5272d4536e24b..2ba05a87619ad29f18954af32e533bf199f42360 100644
--- a/util/test/multiprocess.cc
+++ b/util/test/multiprocess_posix.cc
@@ -153,14 +153,14 @@ pid_t Multiprocess::ChildPID() const {
   return info_->child_pid;
 }
 
-int Multiprocess::ReadPipeFD() const {
+FileHandle Multiprocess::ReadPipeHandle() const {
   int fd = info_->child_pid ? info_->pipe_c2p_read.get()
                             : info_->pipe_p2c_read.get();
   CHECK_NE(fd, -1);
   return fd;
 }
 
-int Multiprocess::WritePipeFD() const {
+FileHandle Multiprocess::WritePipeHandle() const {
   int fd = info_->child_pid ? info_->pipe_p2c_write.get()
                             : info_->pipe_c2p_write.get();
   CHECK_NE(fd, -1);