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

third_party/WebKit/Source/bindings/templates/union_container.h.tmpl

 {% filter format_blink_cpp_source_code %}
 
 {% include 'copyright_block.txt' %}
 #ifndef {{cpp_class}}_h
 #define {{cpp_class}}_h
 
 {% for filename in header_includes %}
 #include "{{filename}}"
 {% endfor %}
 
@@ skipping 48 matching lines @@
 inline void v8SetReturnValue(const CallbackInfo& callbackInfo, {{cpp_class}}& impl) {
   v8SetReturnValue(callbackInfo, ToV8(impl, callbackInfo.Holder(), callbackInfo.GetIsolate()));
 }
 
 template <class CallbackInfo>
 inline void v8SetReturnValue(const CallbackInfo& callbackInfo, {{cpp_class}}& impl, v8::Local<v8::Object> creationContext) {
   v8SetReturnValue(callbackInfo, ToV8(impl, creationContext, callbackInfo.GetIsolate()));
 }
 
 template <>
-struct NativeValueTraits<{{cpp_class}}> {
+struct NativeValueTraits<{{cpp_class}}> : public NativeValueTraitsBase<{{cpp_class}}> {
   {{exported}}static {{cpp_class}} nativeValue(v8::Isolate*, v8::Local<v8::Value>, ExceptionState&);
 };
 
+template <>
+struct V8TypeOf<{{cpp_class}}> {
+  typedef {{v8_class}} Type;
+};
+
 }  // namespace blink
 
 // We need to set canInitializeWithMemset=true because HeapVector supports
 // items that can initialize with memset or have a vtable. It is safe to
 // set canInitializeWithMemset=true for a union type object in practice.
 // See https://codereview.chromium.org/1118993002/#msg5 for more details.
 WTF_ALLOW_MOVE_AND_INIT_WITH_MEM_FUNCTIONS(blink::{{cpp_class}});
 
 #endif  // {{cpp_class}}_h
 
 {% endfilter %}{# format_blink_cpp_source_code #}