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

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

Index: third_party/WebKit/Source/bindings/templates/attributes.cpp
diff --git a/third_party/WebKit/Source/bindings/templates/attributes.cpp b/third_party/WebKit/Source/bindings/templates/attributes.cpp
index e45ecf8f418c59954ccd5f154cb6a74ec9f4a3b4..344d5949669a12366c6aef1f6dda333cd1e9613f 100644
--- a/third_party/WebKit/Source/bindings/templates/attributes.cpp
+++ b/third_party/WebKit/Source/bindings/templates/attributes.cpp
@@ -216,6 +216,15 @@ static v8::experimental::FastAccessorBuilder* {{attribute.name}}AttributeGetterB
 
 
 {##############################################################################}
+{% macro attribute_surrogate_property_callback(attribute) %}
+static v8::Local<v8::Private> {{attribute.name}}SurrogatePropertyCallback(v8::Isolate* isolate)
+{
+    return V8PrivateProperty::get{{attribute.surrogate_property_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)
 {
@@ -499,6 +508,10 @@ bool {{v8_class}}::PrivateScript::{{attribute.name}}AttributeSetter(LocalFrame*
        'V8DOMConfiguration::OnlyExposedToPrivateScript'
        if attribute.only_exposed_to_private_script else
        'V8DOMConfiguration::ExposedToAllScripts' %}
+{% set surrogate_property_callback =
+       '%sV8Internal::%sSurrogatePropertyCallback' % (cpp_class_or_partial, attribute.name)
+       if attribute.is_store_in_field else
+       'nullptr' %}
 {% set holder_check = 'V8DOMConfiguration::DoNotCheckHolder'
        if attribute.is_lenient_this else 'V8DOMConfiguration::CheckHolder' %}
 {% set attribute_configuration_list = [
@@ -508,6 +521,7 @@ bool {{v8_class}}::PrivateScript::{{attribute.name}}AttributeSetter(LocalFrame*
        getter_callback_for_main_world,
        setter_callback_for_main_world,
        getter_builder_callback,
+       surrogate_property_callback,
        wrapper_type_info,
        access_control,
        property_attribute,