Freeze global prototype chain per WebIDL

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 299 matching lines @@
   v8::Local<v8::Signature> signature = v8::Signature::New(isolate, interfaceTemplate);
   ALLOW_UNUSED_LOCAL(signature);
   v8::Local<v8::ObjectTemplate> instanceTemplate = interfaceTemplate->InstanceTemplate();
   ALLOW_UNUSED_LOCAL(instanceTemplate);
   v8::Local<v8::ObjectTemplate> prototypeTemplate = interfaceTemplate->PrototypeTemplate();
   ALLOW_UNUSED_LOCAL(prototypeTemplate);
 
   {%- if interface_name == 'Window' and not is_partial %}{{newline}}
   prototypeTemplate->SetInternalFieldCount(V8Window::internalFieldCount);
   {% endif %}
+  {% if is_immutable_prototype %}{{newline}}
+  // Global object prototype chain consists of Immutable Prototype Exotic Objects
+  prototypeTemplate->SetImmutableProto();
+  {% endif %}
+  {% if is_global %}{{newline}}
+  // Global objects are Immutable Prototype Exotic Objects
+  instanceTemplate->SetImmutableProto();
+  {% endif %}
 
   // Register DOM constants, attributes and operations.
   {% filter runtime_enabled(runtime_enabled_function) %}
   {% if constants %}
   {{install_constants() | indent(2)}}
   {% endif %}
   {% if attributes | has_attribute_configuration %}
   V8DOMConfiguration::installAttributes(isolate, world, instanceTemplate, prototypeTemplate, {{'%sAttributes' % v8_class}}, {{'WTF_ARRAY_LENGTH(%sAttributes)' % v8_class}});
   {% endif %}
   {% if attributes | has_lazy_data_attribute_configuration %}
@@ skipping 145 matching lines @@
 {% for attribute in attributes if attribute.is_implemented_in_private_script %}
 {{attribute_getter_implemented_in_private_script(attribute)}}
 {% if attribute.has_setter %}
 {{attribute_setter_implemented_in_private_script(attribute)}}
 {% endif %}
 {% endfor %}
 {% block partial_interface %}{% endblock %}
 }  // namespace blink
 
 {% endfilter %}{# format_blink_cpp_source_code #}