Plumb whether or not a frame is in shadow DOM to the embedder.

public/web/WebTreeScopeType.h

Index: public/web/WebTreeScopeType.h
diff --git a/public/web/WebTreeScopeType.h b/public/web/WebTreeScopeType.h
new file mode 100644
index 0000000000000000000000000000000000000000..dffc0e91611ab8ed58ea1e7c9bf8003987ae7f91
--- /dev/null
+++ b/public/web/WebTreeScopeType.h
@@ -0,0 +1,20 @@
+// 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 WebTreeScopeType_h
+#define WebTreeScopeType_h
+
+namespace blink {
+
+// Indicates if an item is in the document tree or in a shadow tree, per
+// the Shadow DOM spec at http://www.w3.org/TR/shadow-dom/#shadow-trees.

[hayato, 2015/05/18 05:08:50]

Could you refer to the editor's draft,
http://w3c.github.io/webcomponents/spec/shadow/?

We discourage the link to any published version of the Shadow DOM spec.

[dcheng, 2015/05/18 05:19:14]

Done.

+enum class WebTreeScopeType {
+    Document,
+    Shadow,
+    Last = Shadow,
+};
+
+} // namespace blink
+
+#endif // WebTreeScopeType_h