Reorganize Multiprocess and implement for Windows

util/test/mac/mach_multiprocess.cc

Index: util/test/mac/mach_multiprocess.cc
diff --git a/util/test/mac/mach_multiprocess.cc b/util/test/mac/mach_multiprocess.cc
index ca4e6350322215bb4ee9f7623ad66e9a89a8b6af..9660ee0e4aa4d45aaa4bb389d160719a6216a69b 100644
--- a/util/test/mac/mach_multiprocess.cc
+++ b/util/test/mac/mach_multiprocess.cc
@@ -262,7 +262,7 @@ void MachMultiprocess::MultiprocessChild() {
   // Wait for the parent process to close its end of the pipe. The child process
   // needs to remain alive until then because the parent process will attempt to
   // verify it using the task port it has access to via ChildTask().
-  CheckedReadFileAtEOF(ReadPipeFD());
+  CheckedReadFileAtEOF(ReadPipeHandle());
 
   if (testing::Test::HasFailure()) {
     // Trigger the ScopedForbidReturn destructor.