Implement CSS parser part for ::slotted pseudo element

third_party/WebKit/Source/core/css/parser/CSSSelectorParser.cpp

Index: third_party/WebKit/Source/core/css/parser/CSSSelectorParser.cpp
diff --git a/third_party/WebKit/Source/core/css/parser/CSSSelectorParser.cpp b/third_party/WebKit/Source/core/css/parser/CSSSelectorParser.cpp
index 076f85f14eb4f2913a189c91955f70fb1c273c62..72628a7d539ac7119fe46709b09b4544e7314eba 100644
--- a/third_party/WebKit/Source/core/css/parser/CSSSelectorParser.cpp
+++ b/third_party/WebKit/Source/core/css/parser/CSSSelectorParser.cpp
@@ -23,6 +23,9 @@ static void recordSelectorStats(const CSSParserContext& context, const CSSSelect
             case CSSSelector::PseudoUnresolved:
                 feature = UseCounter::CSSSelectorPseudoUnresolved;
                 break;
+            case CSSSelector::PseudoSlotted:
+                feature = UseCounter::CSSSelectorPseudoSlotted;
+                break;
             case CSSSelector::PseudoContent:
                 feature = UseCounter::CSSSelectorPseudoContent;
                 break;
@@ -374,6 +377,20 @@ PassOwnPtr<CSSParserSelector> CSSSelectorParser::consumePseudo(CSSParserTokenRan
             selector->adoptSelectorVector(selectorVector);
             return selector.release();
         }
+    case CSSSelector::PseudoSlotted:
+        {
+            DisallowPseudoElementsScope scope(this);
+
+            OwnPtr<CSSParserSelector> innerSelector = consumeCompoundSelector(block);
+            block.consumeWhitespace();
+            if (!innerSelector || !block.atEnd())
+                return nullptr;
+            Vector<OwnPtr<CSSParserSelector>> selectorVector;
+            selectorVector.append(innerSelector.release());
+            selector->adoptSelectorVector(selectorVector);
+            selector->setRelationIsAffectedByPseudoSlotted();

[rune, 2016/01/13 09:59:09]

I don't think you need this flag at all, only the ShadowSlot combinator. The
reason we need it for ::content, is that we have explicit combinators in the
selector source and instead of inventing DescendantInsertionPointCrossing,
ChildInsertionPointCrossing, we use Descendant and Child with the
relation-is-affected bit set. In the css text, ::slotted will part of the same
compound as the simple selectors matching the slot, but we introduce a
ShadowSlot combinator and split the compound into two like we do for custom
pseudo elements like in input::-webkit-*.

I've been trying to simplify this splitting process in
https://codereview.chromium.org/1574323003/

[kochi, 2016/01/14 09:02:20]

Acknowledged.

+            return selector.release();
+        }
     case CSSSelector::PseudoLang:
         {
             // FIXME: CSS Selectors Level 4 allows :lang(*-foo)
@@ -567,7 +584,7 @@ const AtomicString& CSSSelectorParser::determineNamespace(const AtomicString& pr
 
 void CSSSelectorParser::prependTypeSelectorIfNeeded(const AtomicString& namespacePrefix, const AtomicString& elementName, CSSParserSelector* compoundSelector)
 {
-    if (elementName.isNull() && defaultNamespace() == starAtom && !compoundSelector->needsImplicitShadowCrossingCombinatorForMatching())
+    if (elementName.isNull() && defaultNamespace() == starAtom && !compoundSelector->needsImplicitShadowCrossingCombinatorForMatching() && !compoundSelector->relationIsAffectedByPseudoSlotted())
         return;
 
     AtomicString determinedElementName = elementName.isNull() ? starAtom : elementName;
@@ -579,8 +596,8 @@ void CSSSelectorParser::prependTypeSelectorIfNeeded(const AtomicString& namespac
     if (compoundSelector->needsImplicitShadowCrossingCombinatorForMatching())
         return rewriteSpecifiersWithElementNameForCustomPseudoElement(tag, compoundSelector, elementName.isNull());
 
-    if (compoundSelector->pseudoType() == CSSSelector::PseudoContent)
-        return rewriteSpecifiersWithElementNameForContentPseudoElement(tag, compoundSelector, elementName.isNull());
+    if (compoundSelector->pseudoType() == CSSSelector::PseudoContent || compoundSelector->pseudoType() == CSSSelector::PseudoSlotted)
+        return rewriteSpecifiersWithElementNameForContentOrSlottedPseudoElement(tag, compoundSelector, elementName.isNull());
 
     // *:host never matches, so we can't discard the * otherwise we can't tell the
     // difference between *:host and just :host.
@@ -615,13 +632,14 @@ void CSSSelectorParser::rewriteSpecifiersWithElementNameForCustomPseudoElement(c
     lastShadowPseudo->setRelation(CSSSelector::ShadowPseudo);
 }
 
-void CSSSelectorParser::rewriteSpecifiersWithElementNameForContentPseudoElement(const QualifiedName& tag, CSSParserSelector* specifiers, bool tagIsImplicit)
+void CSSSelectorParser::rewriteSpecifiersWithElementNameForContentOrSlottedPseudoElement(const QualifiedName& tag, CSSParserSelector* specifiers, bool tagIsImplicit)
 {
     CSSParserSelector* last = specifiers;
     CSSParserSelector* history = specifiers;
     while (history->tagHistory()) {
         history = history->tagHistory();
-        if (history->pseudoType() == CSSSelector::PseudoContent || history->relationIsAffectedByPseudoContent())
+        if (history->pseudoType() == CSSSelector::PseudoContent || history->relationIsAffectedByPseudoContent()
+            || history->pseudoType() == CSSSelector::PseudoSlotted || history->relationIsAffectedByPseudoSlotted())
             last = history;
     }
 
@@ -631,10 +649,10 @@ void CSSSelectorParser::rewriteSpecifiersWithElementNameForContentPseudoElement(
         return;
     }
 
-    // For shadow-ID pseudo-elements to be correctly matched, the ShadowPseudo combinator has to be used.
-    // We therefore create a new Selector with that combinator here in any case, even if matching any (host) element in any namespace (i.e. '*').
     OwnPtr<CSSParserSelector> elementNameSelector = CSSParserSelector::create(tag);
     last->setTagHistory(elementNameSelector.release());
+    if (last->pseudoType() == CSSSelector::PseudoSlotted)
+        last->setRelation(CSSSelector::ShadowSlot);
 }
 
 PassOwnPtr<CSSParserSelector> CSSSelectorParser::addSimpleSelectorToCompound(PassOwnPtr<CSSParserSelector> compoundSelector, PassOwnPtr<CSSParserSelector> simpleSelector)