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 c3a608af70adb86015c653645640c1edcc8eca00..9b022769e96c8d2793211648a2dfed46dad266ad 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;
@@ -471,6 +474,19 @@ 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() || !RuntimeEnabledFeatures::shadowDOMV1Enabled())
+                return nullptr;
+            Vector<OwnPtr<CSSParserSelector>> selectorVector;
+            selectorVector.append(innerSelector.release());
+            selector->adoptSelectorVector(selectorVector);
+            return selector.release();
+        }
     case CSSSelector::PseudoLang:
         {
             // FIXME: CSS Selectors Level 4 allows :lang(*-foo)
@@ -664,7 +680,7 @@ 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->pseudoType() != CSSSelector::PseudoSlotted)
         return;
 
     AtomicString determinedElementName = elementName.isNull() ? starAtom : elementName;
@@ -683,7 +699,7 @@ void CSSSelectorParser::prependTypeSelectorIfNeeded(const AtomicString& namespac
     // ::cue, ::shadow), we need a universal selector to set the combinator
     // (relation) on in the cases where there are no simple selectors preceding
     // the pseudo element.
-    if (tag != anyQName() || compoundSelector->isHostPseudoSelector() || compoundSelector->needsImplicitShadowCrossingCombinatorForMatching())
+    if (tag != anyQName() || compoundSelector->isHostPseudoSelector() || compoundSelector->needsImplicitShadowCrossingCombinatorForMatching() || compoundSelector->pseudoType() == CSSSelector::PseudoSlotted)
         compoundSelector->prependTagSelector(tag, elementName.isNull());
 }
 
@@ -707,17 +723,21 @@ PassOwnPtr<CSSParserSelector> CSSSelectorParser::splitCompoundAtImplicitShadowCr
     // the selector parser as a single compound selector.
     //
     // Example: input#x::-webkit-clear-button -> [ ::-webkit-clear-button, input, #x ]
-
+    //
+    // Likewise, ::slotted() pseudo element has an implicit ShadowSlot combinator to its left
+    // for finding matching slot element in other TreeScope.
+    //
+    // Example: slot[name=foo]::slotted(div) -> [ ::slotted(div), slot, [name=foo] ]
     CSSParserSelector* splitAfter = compoundSelector.get();
 
-    while (splitAfter->tagHistory() && !splitAfter->tagHistory()->needsImplicitShadowCrossingCombinatorForMatching())
+    while (splitAfter->tagHistory() && !splitAfter->tagHistory()->needsImplicitShadowCrossingCombinatorForMatching() && splitAfter->tagHistory()->pseudoType() != CSSSelector::PseudoSlotted)

[rune, 2016/01/19 09:16:09]

You may move the PseudoSlotted into
needsImplicitShadowCrossingCombinatorForMatching() (and possibly drop "Crossing"
from the name, which might yield a better common name).

[kochi, 2016/01/19 11:09:12]

Done.

         splitAfter = splitAfter->tagHistory();
 
     if (!splitAfter || !splitAfter->tagHistory())
         return compoundSelector;
 
     OwnPtr<CSSParserSelector> secondCompound = splitAfter->releaseTagHistory();
-    secondCompound->appendTagHistory(CSSSelector::ShadowPseudo, compoundSelector);
+    secondCompound->appendTagHistory(secondCompound->pseudoType() == CSSSelector::PseudoSlotted ? CSSSelector::ShadowSlot : CSSSelector::ShadowPseudo, compoundSelector);
     return secondCompound.release();
 }