Add <link rel=preconnect> crossorigin attribute (take 2)

public/platform/WebCrossOriginAttribute.h

Index: public/platform/WebCrossOriginAttribute.h
diff --git a/public/platform/WebCrossOriginAttribute.h b/public/platform/WebCrossOriginAttribute.h
new file mode 100644
index 0000000000000000000000000000000000000000..390c605721dfecda1b72d2bf0cd4e03db53621da
--- /dev/null
+++ b/public/platform/WebCrossOriginAttribute.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 WebCrossOriginAttribute_h
+#define WebCrossOriginAttribute_h
+
+namespace blink {
+
+enum CrossOriginAttributeValue {
+    CrossOriginAttributeNotSet,
+    CrossOriginAttributeAnonymous,
+    CrossOriginAttributeUseCredentials,
+};
+
+} // namespace blink
+
+#endif
+