Rename TARGET_OS_* to HOST_OS_*.

runtime/bin/socket.h

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
 #ifndef RUNTIME_BIN_SOCKET_H_
 #define RUNTIME_BIN_SOCKET_H_
 
 #if defined(DART_IO_DISABLED)
 #error "socket.h can only be included on builds with IO enabled"
 #endif
 
 #include "platform/globals.h"
 // Declare the OS-specific types ahead of defining the generic class.
-#if defined(TARGET_OS_ANDROID)
+#if defined(HOST_OS_ANDROID)
 #include "bin/socket_android.h"
-#elif defined(TARGET_OS_FUCHSIA)
+#elif defined(HOST_OS_FUCHSIA)
 #include "bin/socket_fuchsia.h"
-#elif defined(TARGET_OS_LINUX)
+#elif defined(HOST_OS_LINUX)
 #include "bin/socket_linux.h"
-#elif defined(TARGET_OS_MACOS)
+#elif defined(HOST_OS_MACOS)
 #include "bin/socket_macos.h"
-#elif defined(TARGET_OS_WINDOWS)
+#elif defined(HOST_OS_WINDOWS)
 #include "bin/socket_win.h"
 #else
 #error Unknown target os.
 #endif
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
 #include "bin/thread.h"
 #include "bin/utils.h"
 #include "platform/hashmap.h"
@@ skipping 444 matching lines @@
 
   Mutex* mutex_;
 
   DISALLOW_COPY_AND_ASSIGN(ListeningSocketRegistry);
 };
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // RUNTIME_BIN_SOCKET_H_