Add [CachedAccessor] attribute to cache (almost) constant accessors (window.document).

third_party/WebKit/Source/bindings/templates/attributes.cpp.tmpl

 {% from 'utilities.cpp.tmpl' import declare_enum_validation_variable, v8_value_to_local_cpp_value %}
 
 {##############################################################################}
 {% macro attribute_getter(attribute, world_suffix) %}
 static void {{attribute.name}}AttributeGetter{{world_suffix}}(
 {%- if attribute.is_data_type_property %}
 const v8::PropertyCallbackInfo<v8::Value>& info
 {%- else %}
 const v8::FunctionCallbackInfo<v8::Value>& info
 {%- endif %})
@@ skipping 189 matching lines @@
     {% if attribute.has_custom_getter %}
     {{v8_class}}::{{attribute.name}}AttributeGetterCustom(info);
     {% else %}
     {{cpp_class_or_partial}}V8Internal::{{attribute.name}}AttributeGetter{{world_suffix}}(info);
     {% endif %}
 }
 {% endmacro %}
 
 
 {##############################################################################}
+{% macro attribute_cache_property_callback(attribute) %}
+static v8::Local<v8::Private> {{attribute.name}}CachedAccessorCallback(v8::Isolate* isolate)
+{
+    return V8PrivateProperty::get{{attribute.cached_accessor_name}}(isolate).getPrivate();
+}
+{% endmacro %}
+
+
+{##############################################################################}
 {% macro constructor_getter_callback(attribute, world_suffix) %}
 void {{attribute.name}}ConstructorGetterCallback{{world_suffix}}(v8::Local<v8::Name> property, const v8::PropertyCallbackInfo<v8::Value>& info)
 {
     {% if attribute.deprecate_as %}
     Deprecation::countDeprecationIfNotPrivateScript(info.GetIsolate(), currentExecutionContext(info.GetIsolate()), UseCounter::{{attribute.deprecate_as}});
     {% endif %}
     {% if attribute.measure_as %}
     UseCounter::countIfNotPrivateScript(info.GetIsolate(), currentExecutionContext(info.GetIsolate()), UseCounter::{{attribute.measure_as('ConstructorGetter')}});
     {% endif %}
     v8ConstructorAttributeGetter(property, info);
@@ skipping 253 matching lines @@
                         ' | '.join(attribute.access_control_list) %}
 {% else %}
 {% set access_control = 'v8::DEFAULT' %}
 {% endif %}
 {% set property_attribute = 'static_cast<v8::PropertyAttribute>(%s)' %
                             ' | '.join(attribute.property_attributes) %}
 {% set only_exposed_to_private_script =
        'V8DOMConfiguration::OnlyExposedToPrivateScript'
        if attribute.only_exposed_to_private_script else
        'V8DOMConfiguration::ExposedToAllScripts' %}
+{% set cached_accessor_callback =
+       '%sV8Internal::%sCachedAccessorCallback' % (cpp_class_or_partial, attribute.name)
+       if attribute.is_cached_accessor else
+       'nullptr' %}
 {% set holder_check = 'V8DOMConfiguration::DoNotCheckHolder'
        if attribute.is_lenient_this else 'V8DOMConfiguration::CheckHolder' %}
 {% set attribute_configuration_list = [
        '"%s"' % attribute.name,
        getter_callback,
        setter_callback,
        getter_callback_for_main_world,
-       setter_callback_for_main_world,
+       setter_callback_for_main_world,       
+       cached_accessor_callback,
        wrapper_type_info,
        access_control,
        property_attribute,
        only_exposed_to_private_script,
        property_location(attribute),
        holder_check,
    ] %}
 {{'{'}}{{attribute_configuration_list | join(', ')}}{{'}'}}
 {%- endmacro %}