binding: Makes [SaveSameObject] use V8PrivateProperty.

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

Index: third_party/WebKit/Source/bindings/templates/attributes.cpp
diff --git a/third_party/WebKit/Source/bindings/templates/attributes.cpp b/third_party/WebKit/Source/bindings/templates/attributes.cpp
index e253d3276a0c63195123c774152b14157c3b361f..d98e229f172c99ecdf23eed954bc0a9575804d1a 100644
--- a/third_party/WebKit/Source/bindings/templates/attributes.cpp
+++ b/third_party/WebKit/Source/bindings/templates/attributes.cpp
@@ -28,9 +28,15 @@ const v8::FunctionCallbackInfo<v8::Value>& info
     {% endif %}
     {# impl #}
     {% if attribute.is_save_same_object %}
-    v8::Local<v8::String> propertyName = v8AtomicString(info.GetIsolate(), "sameobject_{{attribute.name}}");
+    {% set same_object_private_symbol = 'SameObject' + interface_name + attribute.name[0]|capitalize + attribute.name[1:] %}
+    // If you see a compile error that
+    //   V8PrivateProperty::get{{same_object_private_symbol}}
+    // is not defined, then you need to register your attribute at
+    // V8_PRIVATE_PROPERTY_FOR_EACH defined in V8PrivateProperty.h as
+    //   X(SameObject, {{interface_name}}{{attribute.name[0]|capitalize}}{{attribute.name[1:]}})
+    auto privateSameObject = V8PrivateProperty::getSameObject{{interface_name}}{{attribute.name[0]|capitalize}}{{attribute.name[1:]}}(info.GetIsolate());
     {
-        v8::Local<v8::Value> v8Value = V8HiddenValue::getHiddenValue(ScriptState::current(info.GetIsolate()), holder, propertyName);
+        v8::Local<v8::Value> v8Value = privateSameObject.get(info.GetIsolate()->GetCurrentContext(), holder);
         if (!v8Value.IsEmpty()) {
             v8SetReturnValue(info, v8Value);
             return;
@@ -134,7 +140,7 @@ const v8::FunctionCallbackInfo<v8::Value>& info
     {{attribute.v8_set_return_value}};
     {% endif %}
     {% if attribute.is_save_same_object %}
-    V8HiddenValue::setHiddenValue(ScriptState::current(info.GetIsolate()), holder, propertyName, info.GetReturnValue().Get());
+    privateSameObject.set(info.GetIsolate()->GetCurrentContext(), holder, info.GetReturnValue().Get());
     {% endif %}
 }
 {% endmacro %}