[Bindings] Declare signature and executionContext once

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

 {% filter format_blink_cpp_source_code %}
 
 {% include 'copyright_block.txt' %}
 #include "{{v8_class_or_partial}}.h"
 
 {% for filename in cpp_includes if filename != '%s.h' % cpp_class_or_partial %}
 #include "{{filename}}"
 {% endfor %}
 
 namespace blink {
@@ skipping 696 matching lines @@
 {% block to_impl_with_type_check %}{% endblock %}
 {##############################################################################}
 {% block prepare_prototype_and_interface_object %}
 {% from 'attributes.cpp.tmpl' import install_conditionally_enabled_attributes_on_prototype with context %}
 {% from 'methods.cpp.tmpl' import install_conditionally_enabled_methods with context %}
 {% if has_prepare_prototype_and_interface_object %}
 void {{v8_class_or_partial}}::preparePrototypeAndInterfaceObject(v8::Local<v8::Context> context, const DOMWrapperWorld& world, v8::Local<v8::Object> prototypeObject, v8::Local<v8::Function> interfaceObject, v8::Local<v8::FunctionTemplate> interfaceTemplate) {
   {% if is_partial %}
   {{v8_class}}::preparePrototypeAndInterfaceObject(context, world, prototypeObject, interfaceObject, interfaceTemplate);
   {% endif %}
+
   v8::Isolate* isolate = context->GetIsolate();
+  {% if has_conditional_attributes_on_prototype or methods | conditionally_exposed(is_partial) %}
+  v8::Local<v8::Signature> signature = v8::Signature::New(isolate, interfaceTemplate);
+  ExecutionContext* executionContext = toExecutionContext(context);
+  DCHECK(executionContext);
+  {% endif %}
 
 {% if unscopables %}
   v8::Local<v8::Name> unscopablesSymbol(v8::Symbol::GetUnscopables(isolate));
   v8::Local<v8::Object> unscopables;
   if (v8CallBoolean(prototypeObject->HasOwnProperty(context, unscopablesSymbol)))
     unscopables = prototypeObject->Get(context, unscopablesSymbol).ToLocalChecked().As<v8::Object>();
   else
     unscopables = v8::Object::New(isolate);
   {% for name, runtime_enabled_feature_name in unscopables %}
   {% filter runtime_enabled(runtime_enabled_feature_name) %}
@@ skipping 10 matching lines @@
 {% endif %}
 }
 {% endif %}
 
 {% endblock %}
 {##############################################################################}
 {% block partial_interface %}{% endblock %}
 }  // namespace blink
 
 {% endfilter %}{# format_blink_cpp_source_code #}