Drop [TypeChecking=Nullable]; deduce from attribute type instead

Source/bindings/templates/attributes.cpp

 {##############################################################################}
 {% macro attribute_getter(attribute, world_suffix) %}
 {% filter conditional(attribute.conditional_string) %}
 static void {{attribute.name}}AttributeGetter{{world_suffix}}(
 {%- if attribute.is_expose_js_accessors %}
 const v8::FunctionCallbackInfo<v8::Value>& info
 {%- else %}
 const v8::PropertyCallbackInfo<v8::Value>& info
 {%- endif %})
 {
@@ skipping 27 matching lines @@
     {% if attribute.is_call_with_execution_context %}
     ExecutionContext* executionContext = currentExecutionContext(info.GetIsolate());
     {% endif %}
     {% if attribute.is_call_with_script_state %}
     ScriptState* scriptState = ScriptState::current(info.GetIsolate());
     {% endif %}
     {% if attribute.is_check_security_for_node or
           attribute.is_getter_raises_exception %}
     ExceptionState exceptionState(ExceptionState::GetterContext, "{{attribute.name}}", "{{interface_name}}", holder, info.GetIsolate());
     {% endif %}
-    {% if attribute.is_nullable and not attribute.has_type_checking_nullable %}
+    {% if attribute.is_nullable and not attribute.is_nullable_simple %}
     bool isNull = false;
     {% endif %}
     {% if attribute.cpp_value_original %}
     {{attribute.cpp_type}} {{attribute.cpp_value}}({{attribute.cpp_value_original}});
     {% endif %}
     {# Checks #}
     {% if attribute.is_getter_raises_exception %}
     if (UNLIKELY(exceptionState.throwIfNeeded()))
         return;
     {% endif %}
     {% if attribute.is_check_security_for_node %}
     if (!BindingSecurity::shouldAllowAccessToNode(info.GetIsolate(), {{attribute.cpp_value}}, exceptionState)) {
         v8SetReturnValueNull(info);
         exceptionState.throwIfNeeded();
         return;
     }
     {% endif %}
     {% if attribute.reflect_only %}
     {{release_only_check(attribute.reflect_only, attribute.reflect_missing,
                          attribute.reflect_invalid, attribute.reflect_empty,
                          attribute.cpp_value)
       | indent}}
     {% endif %}
     {% if attribute.is_nullable %}
-    {% if attribute.has_type_checking_nullable %}
+    {% if attribute.is_nullable_simple %}
     if (!{{attribute.cpp_value}}) {
     {% else %}
     if (isNull) {
     {% endif %}
         v8SetReturnValueNull(info);
         return;
     }
     {% endif %}
     {% if attribute.cached_attribute_validation_method %}
     V8HiddenValue::setHiddenValue(info.GetIsolate(), holder, propertyName, {{attribute.cpp_value_to_v8_value}});
@@ skipping 247 matching lines @@
     {% endif %}
     {% if attribute.has_custom_setter %}
     {{v8_class}}::{{attribute.name}}AttributeSetterCustom(v8Value, info);
     {% else %}
     {{cpp_class}}V8Internal::{{attribute.name}}AttributeSetter{{world_suffix}}(v8Value, info);
     {% endif %}
     TRACE_EVENT_SET_SAMPLING_STATE("v8", "V8Execution");
 }
 {% endfilter %}
 {% endmacro %}