WIP bindings: Expand usage of NativeValueTraits.

third_party/WebKit/Source/bindings/core/v8/V8Binding.h

Index: third_party/WebKit/Source/bindings/core/v8/V8Binding.h
diff --git a/third_party/WebKit/Source/bindings/core/v8/V8Binding.h b/third_party/WebKit/Source/bindings/core/v8/V8Binding.h
index 1df7fae7726c68025efbae99fb7607a1ef7a794a..4cc67b2ff436060e9e2edb7141d74f438d08b7b7 100644
--- a/third_party/WebKit/Source/bindings/core/v8/V8Binding.h
+++ b/third_party/WebKit/Source/bindings/core/v8/V8Binding.h
@@ -975,6 +975,7 @@ struct NativeValueTraits<v8::Local<v8::Value>> {
 
 template <>
 struct NativeValueTraits<ScriptValue> {
+  using ImplType = ScriptValue;
   static inline ScriptValue nativeValue(v8::Isolate* isolate,
                                         v8::Local<v8::Value> value,
                                         ExceptionState& exceptionState) {
@@ -982,6 +983,17 @@ struct NativeValueTraits<ScriptValue> {
   }
 };
 
+class Promise;
+template <>
+struct NativeValueTraits<Promise> {
+  using ImplType = ScriptPromise;
+  static inline ScriptPromise nativeValue(v8::Isolate* isolate,
+                                          v8::Local<v8::Value> value,
+                                          ExceptionState& exceptionState) {
+    return ScriptPromise::cast(ScriptState::current(isolate), value);
+  }
+};
+
 template <typename T>
 struct NativeValueTraits<Vector<T>> {
   static inline Vector<T> nativeValue(v8::Isolate* isolate,