Refactor multiprocess test code to allow multiple child processes to be launched.

snapshot/win/process_reader_win_test.cc

 // Copyright 2015 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 67 matching lines @@
 
     // Wait for the parent to signal that it's OK to exit by closing its end of
     // the pipe.
     CheckedReadFileAtEOF(ReadPipeHandle());
   }
 
   DISALLOW_COPY_AND_ASSIGN(ProcessReaderChild);
 };
 
 TEST(ProcessReaderWin, ChildBasic) {
-  ProcessReaderChild process_reader_child;
-  process_reader_child.Run();
+  WinMultiprocess::Run<ProcessReaderChild>();
 }
 
 TEST(ProcessReaderWin, SelfOneThread) {
   ProcessReaderWin process_reader;
   ASSERT_TRUE(process_reader.Initialize(GetCurrentProcess()));
 
   const std::vector<ProcessReaderWin::Thread>& threads =
       process_reader.Threads();
 
   // If other tests ran in this process previously, threads may have been
   // created and may still be running. This check must look for at least one
   // thread, not exactly one thread.
   ASSERT_GE(threads.size(), 1u);
 
   EXPECT_EQ(GetThreadId(GetCurrentThread()), threads[0].id);
 #if defined(ARCH_CPU_64_BITS)
   EXPECT_NE(0, threads[0].context.Rip);
 #else
   EXPECT_NE(0, threads[0].context.Eip);
 #endif
 
   EXPECT_EQ(0, threads[0].suspend_count);
 }
 
 }  // namespace
 }  // namespace test
 }  // namespace crashpad