Add support for new CSS ::slotted() pseudo element

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

Index: third_party/WebKit/Source/core/css/RuleFeature.cpp
diff --git a/third_party/WebKit/Source/core/css/RuleFeature.cpp b/third_party/WebKit/Source/core/css/RuleFeature.cpp
index 76f9b60c3b773d6ff67988f73955cd478a5e8adf..be037d420bdfb0fbd5914e86be16187ea21a79d9 100644
--- a/third_party/WebKit/Source/core/css/RuleFeature.cpp
+++ b/third_party/WebKit/Source/core/css/RuleFeature.cpp
@@ -173,7 +173,8 @@ bool supportsInvalidationWithSelectorList(CSSSelector::PseudoType pseudo)
         || pseudo == CSSSelector::PseudoCue
         || pseudo == CSSSelector::PseudoHost
         || pseudo == CSSSelector::PseudoHostContext
-        || pseudo == CSSSelector::PseudoNot;
+        || pseudo == CSSSelector::PseudoNot
+        || pseudo == CSSSelector::PseudoSlotted;
 }
 
 #endif // ENABLE(ASSERT)
@@ -194,6 +195,9 @@ bool requiresSubtreeInvalidation(const CSSSelector& selector)
     case CSSSelector::PseudoHostContext:
         // :host-context matches a shadow host, yet the simple selectors inside
         // :host-context matches an ancestor of the shadow host.
+    case CSSSelector::PseudoSlotted:
+        // TODO(kochi): This recalculates a bit more than necessary. Find out a way
+        // to avoid unnecessary recalculation.

[rune, 2016/01/09 01:15:36]

This shouldn't be necessary as long as we extract the right invalidation set
features and set insertionPointCrossing correctly below.

         return true;
     default:
         ASSERT(supportsInvalidation(selector.pseudoType()));
@@ -472,7 +476,7 @@ void RuleFeatureSet::addFeaturesToInvalidationSets(const CSSSelector* selector,
         } else {
             if (current->isHostPseudoClass())
                 descendantFeatures.treeBoundaryCrossing = true;
-            if (current->isInsertionPointCrossing())
+            if (current->isInsertionPointCrossing() || current->isSlottedPseudoElement())
                 descendantFeatures.insertionPointCrossing = true;
             if (const CSSSelectorList* selectorList = current->selectorList()) {
                 ASSERT(supportsInvalidationWithSelectorList(current->pseudoType()));