Some Linux and Mac OS event handler refactoring

runtime/bin/eventhandler.h

Index: runtime/bin/eventhandler.h
diff --git a/runtime/bin/eventhandler.h b/runtime/bin/eventhandler.h
index 71df2044c4976c947f0e75d8208bebb319eb107f..156f4d0750ad70b0928965b83a27f8e4560e663e 100644
--- a/runtime/bin/eventhandler.h
+++ b/runtime/bin/eventhandler.h
@@ -7,17 +7,6 @@
 
 #include "bin/builtin.h"
 
-// The event handler delegation class is OS specific.
-#if defined(TARGET_OS_LINUX)
-#include "bin/eventhandler_linux.h"
-#elif defined(TARGET_OS_MACOS)
-#include "bin/eventhandler_macos.h"
-#elif defined(TARGET_OS_WINDOWS)
-#include "bin/eventhandler_win.h"
-#else
-#error Unknown target os.
-#endif
-
 // Flags used to provide information and actions to the eventhandler
 // when sending a message about a file descriptor. These flags should
 // be kept in sync with the constants in socket_impl.dart. For more
@@ -32,6 +21,17 @@ enum MessageFlags {
 };
 
 
+// The event handler delegation class is OS specific.
+#if defined(TARGET_OS_LINUX)
+#include "bin/eventhandler_linux.h"
+#elif defined(TARGET_OS_MACOS)
+#include "bin/eventhandler_macos.h"
+#elif defined(TARGET_OS_WINDOWS)
+#include "bin/eventhandler_win.h"
+#else
+#error Unknown target os.
+#endif
+
 class EventHandler {
  public:
   void SendData(intptr_t id, Dart_Port dart_port, intptr_t data) {