Add the CustomElementsRegistry interface behind the flag

third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.cpp

Index: third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.cpp
diff --git a/third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.cpp b/third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..f22190cea9e0545388421215b5afaafbf2006b51
--- /dev/null
+++ b/third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.cpp
@@ -0,0 +1,29 @@
+// Copyright 2016 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.
+
+#include "core/dom/custom/CustomElementsRegistry.h"
+
+#include "bindings/core/v8/ExceptionState.h"
+#include "bindings/core/v8/ScriptState.h"
+#include "core/dom/ElementRegistrationOptions.h"
+
+namespace blink {
+
+CustomElementsRegistry::CustomElementsRegistry()
+{
+}
+
+void CustomElementsRegistry::define(ScriptState* scriptState,
+    const AtomicString& name, const ScriptValue& constructor,
+    const ElementRegistrationOptions& options, ExceptionState& exceptionState)
+{
+    // TODO(kojii): Element definition process not implemented yet.
+    // http://w3c.github.io/webcomponents/spec/custom/#dfn-element-definition
+}
+
+DEFINE_TRACE(CustomElementsRegistry)
+{
+}
+
+} // namespace blink