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

third_party/WebKit/Source/bindings/templates/interface.cpp.tmpl

Index: third_party/WebKit/Source/bindings/templates/interface.cpp.tmpl
diff --git a/third_party/WebKit/Source/bindings/templates/interface.cpp.tmpl b/third_party/WebKit/Source/bindings/templates/interface.cpp.tmpl
index 133ca77373a359ec16cbbc5ea95efaf6f1e372b4..3d037f89185d9b6db639b90cccbfc117d0743919 100644
--- a/third_party/WebKit/Source/bindings/templates/interface.cpp.tmpl
+++ b/third_party/WebKit/Source/bindings/templates/interface.cpp.tmpl
@@ -854,6 +854,15 @@ v8::Local<v8::Object> {{v8_class}}::findInstanceInPrototypeChain(v8::Local<v8::V
 
 
 {##############################################################################}
+{% block native_value_traits %}
+{{cpp_class}}* NativeValueTraits<{{cpp_class}}>::nativeValue(v8::Isolate* isolate, v8::Local<v8::Value> value, ExceptionState& exceptionState) {
+  return {{v8_class}}::toImplWithTypeCheck(isolate, value);
+}
+
+{% endblock %}
+
+
+{##############################################################################}
 {% block partial_interface %}
 {% if has_partial_interface %}
 {% if needs_runtime_enabled_installer %}