Styling slot fallback content with ::slotted()

third_party/WebKit/Source/core/css/SelectorChecker.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc.
  * All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
@@ skipping 105 matching lines @@
   return context.element->parentElement();
 }
 
 // If context has scope, return slot that matches the scope, otherwise return
 // the assigned slot for scope-less matching of ::slotted pseudo element.
 static const HTMLSlotElement* FindSlotElementInScope(
     const SelectorChecker::SelectorCheckingContext& context) {
   if (!context.scope)
     return context.element->AssignedSlot();
 
-  for (const HTMLSlotElement* slot = context.element->AssignedSlot(); slot;
-       slot = slot->AssignedSlot()) {
+  const HTMLSlotElement* slot = context.element->AssignedSlot();
+  if (!slot)
+    slot = HTMLSlotElement::FindFallbackSlotElementFor(*context.element);
+
+  // Find the slot element that matches the scope.
+  for (; slot; slot = slot->AssignedSlot()) {
     if (slot->GetTreeScope() == context.scope->GetTreeScope())
       return slot;
   }
   return nullptr;
 }
 
 static bool ScopeContainsLastMatchedElement(
     const SelectorChecker::SelectorCheckingContext& context) {
   // If this context isn't scoped, skip checking.
   if (!context.scope)
@@ skipping 1223 matching lines @@
 bool SelectorChecker::MatchesFocusPseudoClass(const Element& element) {
   bool force_pseudo_state = false;
   probe::forcePseudoState(const_cast<Element*>(&element),
                           CSSSelector::kPseudoFocus, &force_pseudo_state);
   if (force_pseudo_state)
     return true;
   return element.IsFocused() && IsFrameFocused(element);
 }
 
 }  // namespace blink