Implement cross-origin attributes using access check interceptors.

third_party/WebKit/Source/bindings/core/v8/V8DOMWrapper.cpp

Index: third_party/WebKit/Source/bindings/core/v8/V8DOMWrapper.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/V8DOMWrapper.cpp b/third_party/WebKit/Source/bindings/core/v8/V8DOMWrapper.cpp
index 598c7849184a513a3d75c786b24541ffefcfd366..e586982e24fcfcd714bdf3d9f573d292f03a21a3 100644
--- a/third_party/WebKit/Source/bindings/core/v8/V8DOMWrapper.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/V8DOMWrapper.cpp
@@ -89,6 +89,15 @@ bool V8DOMWrapper::isWrapper(v8::Isolate* isolate, v8::Local<v8::Value> value) {
   return perIsolateData->hasInstance(untrustedWrapperTypeInfo, object);
 }
 
+void V8DOMWrapper::clearNativeInfo(v8::Isolate* isolate,
+                                   v8::Local<v8::Object> wrapper) {
+  DCHECK_GE(wrapper->InternalFieldCount(), 2);
+  int indices[] = {v8DOMWrapperObjectIndex, v8DOMWrapperTypeIndex};
+  void* values[] = {nullptr, nullptr};
+  wrapper->SetAlignedPointerInInternalFields(WTF_ARRAY_LENGTH(indices), indices,
+                                             values);
+}
+
 bool V8DOMWrapper::hasInternalFieldsSet(v8::Local<v8::Value> value) {
   if (value.IsEmpty() || !value->IsObject())
     return false;