Styling slot fallback content with ::slotted()

third_party/WebKit/Source/core/html/HTMLSlotElement.cpp

Index: third_party/WebKit/Source/core/html/HTMLSlotElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLSlotElement.cpp b/third_party/WebKit/Source/core/html/HTMLSlotElement.cpp
index c86f05d41e11db0268d18643a7845fb9eca588b0..18e7e15b4c32d5b98e81e9c130d712ce2b9c2d82 100644
--- a/third_party/WebKit/Source/core/html/HTMLSlotElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLSlotElement.cpp
@@ -51,6 +51,10 @@ inline HTMLSlotElement::HTMLSlotElement(Document& document)
     : HTMLElement(slotTag, document) {
   UseCounter::Count(document, UseCounter::kHTMLSlotElement);
   SetHasCustomStyleCallbacks();
+  // TODO(kochi): This is required for slot fallback contents to be matched
+  // against ::slotted() pseudo element in a document tree. Remove this once
+  // Shadow DOM V0 code is removed.
+  document.SetShadowCascadeOrder(ShadowCascadeOrder::kShadowCascadeV1);
 }
 
 DEFINE_NODE_FACTORY(HTMLSlotElement);