First implementation of lazily cached accessor for DOM attributes.

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

Index: third_party/WebKit/Source/bindings/templates/attributes.cpp.tmpl
diff --git a/third_party/WebKit/Source/bindings/templates/attributes.cpp.tmpl b/third_party/WebKit/Source/bindings/templates/attributes.cpp.tmpl
index 93dd7c8e93b4aa240283c6c2d70bc6a8232ac12d..698ae1abde2c3fec61c5f3f0f2b07031e5907503 100644
--- a/third_party/WebKit/Source/bindings/templates/attributes.cpp.tmpl
+++ b/third_party/WebKit/Source/bindings/templates/attributes.cpp.tmpl
@@ -257,6 +257,15 @@ v8::Local<v8::Private> {{v8_class_or_partial}}::{{attribute.name}}CachedProperty
 }
 {% endmacro %}
 
+{##############################################################################}
+{% macro attribute_cache_init_callback(attribute) %}
+void {{attribute.name}}CacheInitCallback(v8::Isolate* isolate, v8::Local<v8::Object> holder)
+{
+    auto prop = V8PrivateProperty::Get{{attribute.cached_accessor_name}}(isolate);
+    {{cpp_class}}* impl = {{v8_class}}::toImpl(holder);
+    prop.Set(holder, ToV8({{attribute.cpp_value}}, holder, isolate));
+}
+{% endmacro %}
 
 {##############################################################################}
 {% macro constructor_getter_callback(attribute, world_suffix) %}
@@ -408,6 +417,11 @@ v8::Local<v8::Value> v8Value, const v8::FunctionCallbackInfo<v8::Value>& info
       isolate, "{{cpp_class}}#{{attribute.name.capitalize()}}")
       .DeleteProperty(holder, v8::Undefined(isolate));
   {% endif %}
+
+  {% if attribute.is_lazy_cached_accessor %}
+  // Call cache init callback to store the correct private property.
+  {{attribute.name}}CacheInitCallback(info.GetIsolate(), holder);
+  {% endif %}
 }
 {% endfilter %}{# format_remove_duplicates #}
 {% endmacro %}
@@ -469,7 +483,7 @@ const v8::FunctionCallbackInfo<v8::Value>& info
 
 
 {##############################################################################}
-{% macro attribute_configuration(attribute) %}
+{% macro build_attribute_or_accessor_configuration(attribute, is_attribute_configuration) %}
 {% from 'utilities.cpp.tmpl' import property_location %}
 {% if attribute.constructor_type %}
   {% if attribute.needs_constructor_getter_callback %}
@@ -491,10 +505,15 @@ const v8::FunctionCallbackInfo<v8::Value>& info
        if attribute.constructor_type else 'nullptr' %}
 {% set property_attribute = 'static_cast<v8::PropertyAttribute>(%s)' %
                             ' | '.join(attribute.property_attributes) %}
-{% set cached_accessor_callback =
+{% set cached_property_key =
        '%s::%sCachedPropertyKey' % (v8_class_or_partial, attribute.name)
        if attribute.is_cached_accessor else
        'nullptr' %}
+{% set cache_init_callback =
+      '%sV8Internal::%sCacheInitCallback' %
+          (cpp_class_or_partial, attribute.name)
+       if attribute.is_lazy_cached_accessor else
+       'nullptr' %}
 {% set holder_check = 'V8DOMConfiguration::kDoNotCheckHolder'
        if attribute.is_lenient_this else 'V8DOMConfiguration::kCheckHolder' %}
 {% if attribute.is_per_world_bindings %}
@@ -502,12 +521,62 @@ const v8::FunctionCallbackInfo<v8::Value>& info
 {% set setter_callback_for_main_world =
        '%sForMainWorld' % setter_callback
        if attribute.has_setter else 'nullptr' %}
-{"{{attribute.name}}", {{getter_callback_for_main_world}}, {{setter_callback_for_main_world}}, {{cached_accessor_callback}}, {{wrapper_type_info}}, {{property_attribute}}, {{property_location(attribute)}}, {{holder_check}}, V8DOMConfiguration::kMainWorld},
-{"{{attribute.name}}", {{getter_callback}}, {{setter_callback}}, {{cached_accessor_callback}}, {{wrapper_type_info}}, {{property_attribute}}, {{property_location(attribute)}}, {{holder_check}}, V8DOMConfiguration::kNonMainWorlds}
-{%- else %}
-{"{{attribute.name}}", {{getter_callback}}, {{setter_callback}}, {{cached_accessor_callback}}, {{wrapper_type_info}}, {{property_attribute}}, {{property_location(attribute)}}, {{holder_check}}, V8DOMConfiguration::kAllWorlds}
-{%- endif %}
-{%- endmacro %}
+{% endif %}
+
+
+{% set config_pre = {
+  "main" : [
+         '"%s"' % attribute.name,
+         getter_callback_for_main_world,
+         setter_callback_for_main_world,
+       ],
+  "non_main" : [
+         '"%s"' % attribute.name,
+         getter_callback,
+         setter_callback,
+       ],
+} %}
+
+{% set accessor_only_fields = [] if is_attribute_configuration else [
+      cached_property_key,
+      cache_init_callback,
+] %}
+
+{% set config_post = [
+       wrapper_type_info,
+       property_attribute,
+       property_location(attribute),
+       holder_check,
+] %}
+
+{% if attribute.is_per_world_bindings %}
+  {% set main_config_list = config_pre["main"] + accessor_only_fields +
+      config_post + ['V8DOMConfiguration::kMainWorld'] %}
+  {% set non_main_config_list = config_pre["non_main"] + accessor_only_fields +
+      config_post + ['V8DOMConfiguration::kNonMainWorlds'] %}
+  {# Emit for main world then non-main.#}
+  {{'{'}}{{main_config_list | join(', ')}}{{'}'}}
+  {{','}}
+  {{'{'}}{{non_main_config_list | join(', ')}}{{'}'}}
+{% else %}
+  {% set all_worlds_config_list = config_pre["non_main"] + accessor_only_fields +
+      config_post + ['V8DOMConfiguration::kAllWorlds'] %}
+  {# Emit only for all worlds #}
+  {{'{'}}{{all_worlds_config_list | join(', ')}}{{'}'}}
+{% endif %}
+{% endmacro %}
+
+{##############################################################################}
+{% macro attribute_configuration(attribute) %}
+{% set is_attribute_configuration = true %}
+{{build_attribute_or_accessor_configuration(attribute, is_attribute_configuration)}}
+{% endmacro %}
+
+{##############################################################################}
+{% macro accessor_configuration(attribute) %}
+{% set is_attribute_configuration = false %}
+{{build_attribute_or_accessor_configuration(attribute, is_attribute_configuration)}}
+{% endmacro %}
 
 {##############################################################################}
 {% macro install_conditionally_enabled_attributes_on_prototype() %}
@@ -516,7 +585,7 @@ const v8::FunctionCallbackInfo<v8::Value>& info
 {% filter secure_context(attribute.secure_context_test) %}
 {% filter runtime_enabled(attribute.runtime_enabled_feature_name) %}
 static const V8DOMConfiguration::AccessorConfiguration accessorConfiguration[] = {
-  {{attribute_configuration(attribute)}}
+  {{accessor_configuration(attribute)}}
 };
 for (const auto& accessorConfig : accessorConfiguration)
   V8DOMConfiguration::InstallAccessor(isolate, world, v8::Local<v8::Object>(), prototypeObject, interfaceObject, signature, accessorConfig);