Mojo C++ bindings: share DataView class between chromium and blink variants.

mojo/public/tools/bindings/generators/cpp_templates/union_traits_definition.tmpl

 {%- set mojom_type = union|get_qualified_name_for_kind %}
 
 // static
 bool UnionTraits<{{mojom_type}}::DataView, {{mojom_type}}Ptr>::Read(
     {{mojom_type}}::DataView input,
     {{mojom_type}}Ptr* output) {
   *output = {{mojom_type}}::New();
   {{mojom_type}}Ptr& result = *output;
 
   internal::UnionAccessor<{{mojom_type}}> result_acc(result.get());
   switch (input.tag()) {
 {%- for field in union.fields %}
     case {{mojom_type}}::Tag::{{field.name|upper}}: {
 {%-   set name = field.name %}
 {%-   set kind = field.kind %}
 {%-   set serializer_type = kind|unmapped_type_for_serializer %}
 {%-   if kind|is_object_kind %}
       result_acc.SwitchActive({{mojom_type}}::Tag::{{name|upper}});
       if (!input.Read{{name|under_to_camel}}(result_acc.data()->{{name}}))
         return false;
 
-{%-   elif kind|is_any_handle_or_interface_kind %}
+{%-   elif kind|is_any_handle_kind %}
       auto result_{{name}} = input.Take{{name|under_to_camel}}();
       result->set_{{name}}(std::move(result_{{name}}));
 
+{%-   elif kind|is_any_interface_kind %}
+      auto result_{{name}} =
+          input.Take{{name|under_to_camel}}<typename std::remove_reference<decltype(result->get_{{name}}())>::type>();
+      result->set_{{name}}(std::move(result_{{name}}));
+
 {%-   elif kind|is_enum_kind %}
       decltype(result->get_{{name}}()) result_{{name}};
       if (!input.Read{{name|under_to_camel}}(&result_{{name}}))
         return false;
       result->set_{{name}}(result_{{name}});
 
 {%-   else %}
       result->set_{{name}}(input.{{name}}());
 {%-   endif %}
       break;
     }
 {%- endfor %}
     default:
       return false;
   }
   return true;
 }