Reorganize Multiprocess and implement for Windows

util/test/mac/mach_multiprocess.cc

 // Copyright 2014 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 244 matching lines @@
   info_->remote_port.reset();
   info_->local_port.reset();
 
   // Close the write pipe now, for cases where the parent is waiting on it to
   // be closed as an indication that the child has finished.
   CloseWritePipe();
 
   // 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.
     return;
   }
 
   forbid_return.Disarm();
 }
 
 }  // namespace test
 }  // namespace crashpad