Freeze global prototype chain per WebIDL

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

Index: third_party/WebKit/Source/bindings/templates/interface.cpp.tmpl
diff --git a/third_party/WebKit/Source/bindings/templates/interface.cpp.tmpl b/third_party/WebKit/Source/bindings/templates/interface.cpp.tmpl
index 634910bded1901de56b61201e87020d81099dca7..86e2d881e4c3c2f62f3139a03e6ff1acb2062677 100644
--- a/third_party/WebKit/Source/bindings/templates/interface.cpp.tmpl
+++ b/third_party/WebKit/Source/bindings/templates/interface.cpp.tmpl
@@ -793,6 +793,8 @@ v8::Local<v8::FunctionTemplate> {{v8_class}}::domTemplateForNamedPropertiesObjec
 
     v8::Local<v8::ObjectTemplate> namedPropertiesObjectTemplate = namedPropertiesObjectFunctionTemplate->PrototypeTemplate();
     namedPropertiesObjectTemplate->SetInternalFieldCount({{v8_class}}::internalFieldCount);
+    // Named Properties object has SetPrototype method of Immutable Prototype Exotic Objects
+    namedPropertiesObjectTemplate->SetImmutableProto();
     V8DOMConfiguration::setClassString(isolate, namedPropertiesObjectTemplate, "{{interface_name}}Properties");
     {{install_named_property_handler('namedPropertiesObjectTemplate') | indent}}