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 5d78d197e69acccb7802a4b3ec9512ae298be337..e97742713c41d82d94828e6879e82a48f6251db9 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);