Allow using SelectorQuery fast paths in quirks mode and disconnected subtrees.

third_party/WebKit/Source/core/dom/SelectorQuery.h

 /*
  * Copyright (C) 2011, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2014 Samsung Electronics. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 63 matching lines @@
     unsigned slow_traversing_shadow_tree_scan;
   };
   // Used by unit tests to get information about what paths were taken during
   // the last query. Always reset between queries. This system is disabled in
   // non DCHECK builds to avoid the overhead on the query process.
   static QueryStats LastQueryStats();
 
  private:
   explicit SelectorQuery(CSSSelectorList);
 
-  bool CanUseFastQuery(const ContainerNode& root_node) const;
-
   template <typename SelectorQueryTrait>
   void ExecuteWithId(ContainerNode& root_node,
                      typename SelectorQueryTrait::OutputType&) const;
   template <typename SelectorQueryTrait>
   void FindTraverseRootsAndExecute(
       ContainerNode& root_node,
       typename SelectorQueryTrait::OutputType&) const;
   template <typename SelectorQueryTrait>
   void ExecuteForTraverseRoot(ContainerNode& traverse_root,
                               ContainerNode& root_node,
@@ skipping 15 matching lines @@
   // Contains the list of CSSSelector's to match, but without ones that could
   // never match like pseudo elements, div::before. This can be empty, while
   // m_selectorList will never be empty as SelectorQueryCache::add would have
   // thrown an exception.
   Vector<const CSSSelector*> selectors_;
   AtomicString selector_id_;
   bool selector_id_is_rightmost_ : 1;
   bool selector_id_affected_by_sibling_combinator_ : 1;
   bool uses_deep_combinator_or_shadow_pseudo_ : 1;
   bool needs_updated_distribution_ : 1;
+  bool use_slow_scan_ : 1;
 };
 
 class SelectorQueryCache {
   USING_FAST_MALLOC(SelectorQueryCache);
 
  public:
   SelectorQuery* Add(const AtomicString&, const Document&, ExceptionState&);
   void Invalidate();
 
  private:
   HashMap<AtomicString, std::unique_ptr<SelectorQuery>> entries_;
 };
 
 }  // namespace blink
 
 #endif