Implement matching part of ::slotted() pseudo element

third_party/WebKit/Source/core/css/SelectorFilter.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 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/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 116 matching lines @@
     default:
         break;
     }
 }
 
 void SelectorFilter::collectIdentifierHashes(const CSSSelector& selector, unsigned* identifierHashes, unsigned maximumIdentifierCount)
 {
     unsigned* hash = identifierHashes;
     unsigned* end = identifierHashes + maximumIdentifierCount;
     CSSSelector::Relation relation = selector.relation();
-    bool relationIsAffectedByPseudoContent = selector.relationIsAffectedByPseudoContent();
+    bool relationIsAffectedByPseudoContentOrSlotted = selector.relationIsAffectedByPseudoContent() || selector.pseudoType() == CSSSelector::PseudoSlotted;

[rune, 2016/01/20 12:53:32]

I think this code is a bit more advanced than it needs to. Here we could have
done an early return like this:

if (selector.relationIsAffectedByPseudoContent())
    return;

[kochi, 2016/01/21 05:09:37]

Done.

 
     // Skip the topmost selector. It is handled quickly by the rule hashes.
     bool skipOverSubselectors = true;
     for (const CSSSelector* current = selector.tagHistory(); current; current = current->tagHistory()) {
         // Only collect identifiers that match ancestors.
         switch (relation) {
         case CSSSelector::SubSelector:
             if (!skipOverSubselectors)
                 collectDescendantSelectorIdentifierHashes(*current, hash);
             break;
         case CSSSelector::DirectAdjacent:
         case CSSSelector::IndirectAdjacent:
             skipOverSubselectors = true;
             break;
         case CSSSelector::Descendant:
         case CSSSelector::Child:
-            if (relationIsAffectedByPseudoContent) {
+        case CSSSelector::ShadowSlot:
+            if (relationIsAffectedByPseudoContentOrSlotted) {
                 // Disable fastRejectSelector.
                 *identifierHashes = 0;
                 return;
             }
             // Fall through.

[rune, 2016/01/20 12:53:32]

I don't think there's a need to wait for the next round in the loop to do this.

There's no big deal if we return no hashes in the case for non-matching
selectors like "::content + div" or "::content ~ div". I think you can replace
the code from "case CSSSelector::Descendant:" down here with:

case CSSSelector::ShadowSlot:
    *identifierHashes = 0;
    return;
case CSSSelector::Descendant:
case CSSSelector::Child:

[kochi, 2016/01/21 05:09:37]

Done.

         case CSSSelector::ShadowPseudo:
         case CSSSelector::ShadowDeep:
             skipOverSubselectors = false;
             collectDescendantSelectorIdentifierHashes(*current, hash);
             break;
-        case CSSSelector::ShadowSlot:
-            // TODO(kochi): Add this in later CL.
-            break;
         }
         if (hash == end)
             return;
         relation = current->relation();
-        relationIsAffectedByPseudoContent = current->relationIsAffectedByPseudoContent();
+        relationIsAffectedByPseudoContentOrSlotted = current->relationIsAffectedByPseudoContent() || current->pseudoType() == CSSSelector::PseudoSlotted;

[rune, 2016/01/20 12:53:32]

This can be replaced with:

if (current->relationIsAffectedByPseudoContent()) {
    *identifierHashes = 0;
    return;
}

[kochi, 2016/01/21 05:09:37]

Done.

     }
     *hash = 0;
 }
 
 DEFINE_TRACE(SelectorFilter::ParentStackFrame)
 {
     visitor->trace(element);
 }
 
 DEFINE_TRACE(SelectorFilter)
 {
 #if ENABLE(OILPAN)
     visitor->trace(m_parentStack);
 #endif
 }
 
 }