| Index: third_party/WebKit/Source/core/dom/Element.cpp | 
| diff --git a/third_party/WebKit/Source/core/dom/Element.cpp b/third_party/WebKit/Source/core/dom/Element.cpp | 
| index 7003675a5570233f05ad4e4d54e441ca8274acd1..162ad6d1f46d58aed4985274b031c7cb4d8d7040 100644 | 
| --- a/third_party/WebKit/Source/core/dom/Element.cpp | 
| +++ b/third_party/WebKit/Source/core/dom/Element.cpp | 
| @@ -1952,6 +1952,8 @@ PassRefPtrWillBeRawPtr<ShadowRoot> Element::attachShadow(const ScriptState* scri | 
| return nullptr; | 
| } | 
|  | 
| +    document().setUseCascadeOrderForShadowDOMV1(); | 
| + | 
| ShadowRootType type = ShadowRootType::V0; | 
| if (shadowRootInitDict.hasMode()) | 
| type = shadowRootInitDict.mode() == "open" ? ShadowRootType::Open : ShadowRootType::Closed; | 
|  |