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

third_party/WebKit/Source/bindings/tests/results/core/DoubleOrString.h

Index: third_party/WebKit/Source/bindings/tests/results/core/DoubleOrString.h
diff --git a/third_party/WebKit/Source/bindings/tests/results/core/DoubleOrString.h b/third_party/WebKit/Source/bindings/tests/results/core/DoubleOrString.h
index 8938fb0ccf1aeaa1cb911d4b406dda9206e4990c..cb995e01b301a4f6b84c5d0628030240269601b4 100644
--- a/third_party/WebKit/Source/bindings/tests/results/core/DoubleOrString.h
+++ b/third_party/WebKit/Source/bindings/tests/results/core/DoubleOrString.h
@@ -14,6 +14,7 @@
 
 #include "bindings/core/v8/Dictionary.h"
 #include "bindings/core/v8/ExceptionState.h"
+#include "bindings/core/v8/NativeValueTraits.h"
 #include "bindings/core/v8/V8Binding.h"
 #include "core/CoreExport.h"
 #include "platform/heap/Handle.h"
@@ -73,10 +74,15 @@ inline void v8SetReturnValue(const CallbackInfo& callbackInfo, DoubleOrString& i
 }
 
 template <>
-struct NativeValueTraits<DoubleOrString> {
+struct NativeValueTraits<DoubleOrString> : public NativeValueTraitsBase<DoubleOrString> {
   CORE_EXPORT static DoubleOrString nativeValue(v8::Isolate*, v8::Local<v8::Value>, ExceptionState&);
 };
 
+template <>
+struct V8TypeOf<DoubleOrString> {
+  typedef V8DoubleOrString Type;
+};
+
 }  // namespace blink
 
 // We need to set canInitializeWithMemset=true because HeapVector supports