Bindings: Fix template parameter in NativeValueTraits<UnionBase>

UnionBase is passed by value, so NativeValueTraits should handle it
not as a pointer.


Bug: 839389
Change-Id: I0a6ca6892bb8ec041376907bf3e5ccd92b797f49
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2015867Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Commit-Queue: Hitoshi Yoshida <peria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#734354}

third_party/blink/renderer/bindings/core/v8/native_value_traits_impl.h

@@ -795,7 +795,7 @@ template <typename T>
 struct NativeValueTraits<
     T,
     typename std::enable_if_t<std::is_base_of<bindings::UnionBase, T>::value>>
-    : public NativeValueTraitsBase<T*> {
+    : public NativeValueTraitsBase<T> {
   static T NativeValue(v8::Isolate* isolate,
                        v8::Local<v8::Value> value,
                        ExceptionState& exception_state) {