Add mips skeleton sources.

runtime/vm/cpu_mips.cc

Index: runtime/vm/cpu_mips.cc
===================================================================
--- runtime/vm/cpu_mips.cc	(revision 0)
+++ runtime/vm/cpu_mips.cc	(revision 0)
@@ -0,0 +1,29 @@
+// 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.
+
+#include "vm/globals.h"
+
+#if defined(TARGET_ARCH_MIPS)
+
+#if defined(HOST_ARCH_MIPS)
+#include <sys/syscall.h>  /* NOLINT */
+#include <unistd.h>  /* NOLINT */
+#endif
+
+#include "vm/cpu.h"
+
+namespace dart {
+
+void CPU::FlushICache(uword start, uword size) {
+  UNIMPLEMENTED();
+}
+
+
+const char* CPU::Id() {
+  return "mips";
+}
+
+}  // namespace dart
+
+#endif  // defined TARGET_ARCH_MIPS