[bindings] Implement an ExperimentEnabled IDL extended attribute.

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

Index: third_party/WebKit/Source/bindings/templates/constants.cpp
diff --git a/third_party/WebKit/Source/bindings/templates/constants.cpp b/third_party/WebKit/Source/bindings/templates/constants.cpp
index bac23ca38f6fa129543b54c134c7c6d3b8336fa0..e71d7647a35574eb4e92886bb18a01befc3f2434 100644
--- a/third_party/WebKit/Source/bindings/templates/constants.cpp
+++ b/third_party/WebKit/Source/bindings/templates/constants.cpp
@@ -48,6 +48,13 @@ V8DOMConfiguration::installConstant(isolate, functionTemplate, prototypeTemplate
 {% for constant in special_getter_constants %}
 V8DOMConfiguration::installConstantWithGetter(isolate, functionTemplate, prototypeTemplate, "{{constant.name}}", {{cpp_class}}V8Internal::{{constant.name}}ConstantGetterCallback);
 {% endfor %}
+{# Constants with [ExperimentEnabled] only #}
+{% for constant in experimental_only_constants %}
+if (Experiments::isApiEnabled(ec, "{{constant['api_experiment_name']}}")) {
+    const V8DOMConfiguration::ConstantConfiguration constant{{constant.name}}Configuration = {{constant_configuration(constant)}};
+    V8DOMConfiguration::installConstant(isolate, functionTemplate, prototypeTemplate, constant{{constant.name}}Configuration);
+}
+{% endfor %}
 {# Check constants #}
 {% if not do_not_check_constants %}
 {% for constant in constants %}