[bindings] Introduce ScriptValue.to<T> to convert to native values.

Source/bindings/core/v8/NativeValueTraits.h

+// Copyright (c) 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 NativeValueTraits_h
+#define NativeValueTraits_h
+
+namespace v8 {

[Yuki, 2015/03/16 08:03:07]

You'd better include <v8.h>, which is a third party library from our point of
view.

[vivekg, 2015/03/16 08:32:17]

Done.

+class Isolate;
+template <typename T>
+class Local;
+class Value;
+} // namespace v8
+
+namespace blink {
+
+class ExceptionState;
+
+template <typename T>
+struct NativeValueTraits {
+    static T nativeValue(const v8::Local<v8::Value>&, v8::Isolate*, ExceptionState&);

[Yuki, 2015/03/16 08:03:07]

I'm not quite sure why this has been const v8::Local&.

I think v8::Local is defined as being able to pass it as a value, and we pass it
as a value everywhere else.

[vivekg, 2015/03/16 08:32:17]

I will take this up as follow up patch.

+};
+
+} // namespace blink
+
+#endif // NativeValueTraits_h