Introduce infrastructure for tracing ScriptWrappables.

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

 {% extends 'interface_base.cpp' %}
 
 
 {##############################################################################}
 {% block indexed_property_getter %}
 {% if indexed_property_getter and not indexed_property_getter.is_custom %}
 {% set getter = indexed_property_getter %}
 static void indexedPropertyGetter(uint32_t index, const v8::PropertyCallbackInfo<v8::Value>& info)
 {
     {{cpp_class}}* impl = {{v8_class}}::toImpl(info.Holder());
@@ skipping 516 matching lines @@
         return;
     }
     {# No match, throw error #}
     exceptionState.throwTypeError("No matching constructor signature.");
     exceptionState.throwIfNeeded();
 }
 
 {% endif %}
 {% endblock %}
 
+{##############################################################################}
+
+{% block trace_wrapper_references %}
+{% if trace_wrapper_references %}
+DEFINE_TRACE_WRAPPERS({{cpp_class_or_partial}})
+{
+    {% for traceable in trace_wrapper_references %}
+    visitor->traceWrappers({{traceable}}());
+    {% endfor %}
+
+    {% if parent_interface %}
+    {{parent_interface}}::traceWrappers(visitor);
+    {% endif %}
+}
+{% endif %}
+{% endblock %}
 
 {##############################################################################}
+
 {% block visit_dom_wrapper %}
 {% if set_wrapper_reference_from or set_wrapper_reference_to %}
 void {{v8_class}}::visitDOMWrapper(v8::Isolate* isolate, ScriptWrappable* scriptWrappable, const v8::Persistent<v8::Object>& wrapper)
 {
     {{cpp_class}}* impl = scriptWrappable->toImpl<{{cpp_class}}>();
     {% if set_wrapper_reference_to %}
     v8::Local<v8::Object> context = v8::Local<v8::Object>::New(isolate, wrapper);
     v8::Context::Scope scope(context->CreationContext());
     {{set_wrapper_reference_to.cpp_type}} {{set_wrapper_reference_to.name}} = impl->{{set_wrapper_reference_to.name}}();
     if ({{set_wrapper_reference_to.name}}) {
@@ skipping 385 matching lines @@
 
 {% for method in methods if method.overloads and method.overloads.has_partial_overloads %}
 void {{v8_class}}::register{{method.name | blink_capitalize}}MethodForPartialInterface(void (*method)(const v8::FunctionCallbackInfo<v8::Value>&))
 {
     {{cpp_class}}V8Internal::{{method.name}}MethodForPartialInterface = method;
 }
 
 {% endfor %}
 {% endif %}
 {% endblock %}