bindings: Add C++ versions of WebIDL types and generalize NativeValueTraits.

third_party/WebKit/Source/bindings/core/v8/IDLTypesBase.h

Index: third_party/WebKit/Source/bindings/core/v8/IDLTypesBase.h
diff --git a/third_party/WebKit/Source/bindings/core/v8/IDLTypesBase.h b/third_party/WebKit/Source/bindings/core/v8/IDLTypesBase.h
new file mode 100644
index 0000000000000000000000000000000000000000..96a24515970341f4bb10103a9ca088860d48dfaf
--- /dev/null
+++ b/third_party/WebKit/Source/bindings/core/v8/IDLTypesBase.h
@@ -0,0 +1,24 @@
+// Copyright (c) 2017 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 IDLTypesBase_h
+#define IDLTypesBase_h
+
+namespace blink {
+
+// This is the base type for all WebIDL types, such as the ones defined in
+// IDLTypes.h. It is defined in a separate location to avoid circular header
+// inclusions when one only needs to check if a type inherits from IDLBase.
+struct IDLBase {
+  using ImplType = void;
+};
+
+template <typename T>
+struct IDLBaseHelper : public IDLBase {

[haraken, 2017/03/06 12:56:32]

Why do we need to distinguish IDLBaseHelper from IDLBase? Is it related to the
circular header inclusion you mentioned in the above?

[Raphael Kubo da Costa (rakuco), 2017/03/06 14:29:17]

Having IDLBase itself be a template class does not make much semantic sense:
IDLSequence and IDLRecord would need to inherit from IDLBase<T>, for some T that
is unrelated to them.

+  using ImplType = T;
+};
+
+}  // namespace blink
+
+#endif  // IDLTypesBase_h