Added <link rel=preconnect> crossorigin attribute

Source/core/html/CrossOriginAttribute.h

Index: Source/core/html/CrossOriginAttribute.h
diff --git a/Source/core/html/CrossOriginAttribute.h b/Source/core/html/CrossOriginAttribute.h
new file mode 100644
index 0000000000000000000000000000000000000000..480803cf792b63ddae6dd4d1fcdc09a6a6ea08b9
--- /dev/null
+++ b/Source/core/html/CrossOriginAttribute.h
@@ -0,0 +1,19 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CrossOriginAttribute_h
+#define CrossOriginAttribute_h
+
+#include "public/platform/WebCrossOriginAttribute.h"
+#include "wtf/text/WTFString.h"
+
+namespace blink {
+
+CrossOriginAttributeValue crossOriginAttributeValue(const String& value);
+
+} // namespace blink
+
+#endif
+
+