dart:io | Add Link class, as sibling to File and Directory.

runtime/bin/file_win.cc

Index: runtime/bin/file_win.cc
diff --git a/runtime/bin/file_win.cc b/runtime/bin/file_win.cc
index 1c22ededcf24a42cf4e9f11b88c82581a71948d3..2d6dae865db706d09dbabf84c8f6cf2acb72916b 100644
--- a/runtime/bin/file_win.cc
+++ b/runtime/bin/file_win.cc
@@ -154,6 +154,12 @@ bool File::Create(const char* name) {
 }
 
 
+bool File::CreateLink(const char* name, const char* target) {
+  // TODO(whesse): Implement Junction creation.
+  return false;
+}
+
+
 bool File::Delete(const char* name) {
   const wchar_t* system_name = StringUtils::Utf8ToWide(name);
   int status = _wremove(system_name);