Styling slot fallback content with ::slotted()

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

 /*
  * Copyright (C) 2015 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 33 matching lines @@
 #include "core/probe/CoreProbes.h"
 
 namespace blink {
 
 using namespace HTMLNames;
 
 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);
 
 // static
 AtomicString HTMLSlotElement::NormalizeSlotName(const AtomicString& name) {
   return (name.IsNull() || name.IsEmpty()) ? g_empty_atom : name;
 }
 
 const HeapVector<Member<Node>>& HTMLSlotElement::AssignedNodes() {
@@ skipping 298 matching lines @@
 
 DEFINE_TRACE(HTMLSlotElement) {
   visitor->Trace(assigned_nodes_);
   visitor->Trace(distributed_nodes_);
   visitor->Trace(old_distributed_nodes_);
   visitor->Trace(distributed_indices_);
   HTMLElement::Trace(visitor);
 }
 
 }  // namespace blink