Prepare for removal of source_filter.gypi:

runtime/bin/process_win.cc

Index: runtime/bin/process_win.cc
===================================================================
--- runtime/bin/process_win.cc	(revision 18775)
+++ runtime/bin/process_win.cc	(working copy)
@@ -2,15 +2,17 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-#include <process.h>
+#include "platform/globals.h"
+#if defined(TARGET_OS_WINDOWS)
 
+#include <process.h>  // NOLINT
+
 #include "bin/builtin.h"
 #include "bin/process.h"
 #include "bin/eventhandler.h"
 #include "bin/log.h"
 #include "bin/thread.h"
 #include "bin/utils.h"
-#include "platform/globals.h"
 
 static const int kReadHandle = 0;
 static const int kWriteHandle = 1;
@@ -660,3 +662,5 @@
 intptr_t Process::CurrentProcessId() {
   return static_cast<intptr_t>(GetCurrentProcessId());
 }
+
+#endif  // defined(TARGET_OS_WINDOWS)