Introduce infrastructure for tracing ScriptWrappables.

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

Index: third_party/WebKit/Source/bindings/templates/interface.cpp
diff --git a/third_party/WebKit/Source/bindings/templates/interface.cpp b/third_party/WebKit/Source/bindings/templates/interface.cpp
index 3e522fa757dc7e986e91c68d60805c402d86bdd9..c60125870a0c95e5b835b82a674562de6741ea5e 100644
--- a/third_party/WebKit/Source/bindings/templates/interface.cpp
+++ b/third_party/WebKit/Source/bindings/templates/interface.cpp
@@ -534,8 +534,25 @@ static void constructor(const v8::FunctionCallbackInfo<v8::Value>& info)
 {% endif %}
 {% endblock %}
 
+{##############################################################################}
+
+{% block trace_wrapper_references %}
+{% if trace_wrapper_references %}
+DEFINE_TRACE_WRAPPERS({{cpp_class_or_partial}})
+{
+    {% for traceable in trace_wrapper_references %}
+    visitor->trace({{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)