Tentative: clean up applyAuthorStyles

Source/core/css/ElementRuleCollector.cpp

Index: Source/core/css/ElementRuleCollector.cpp
diff --git a/Source/core/css/ElementRuleCollector.cpp b/Source/core/css/ElementRuleCollector.cpp
index e421fbb7e5f520afda79d359612f3b52af914737..d8fe6cd80bd5b875960b72a7fb342b72680251f7 100644
--- a/Source/core/css/ElementRuleCollector.cpp
+++ b/Source/core/css/ElementRuleCollector.cpp
@@ -118,14 +118,12 @@ void ElementRuleCollector::addElementStyleProperties(const StylePropertySet* pro
         m_result.isCacheable = false;
 }
 
-static bool rulesApplicableInCurrentTreeScope(const Element* element, const ContainerNode* scopingNode, bool elementApplyAuthorStyles)
+static bool rulesApplicableInCurrentTreeScope(const Element* element, const ContainerNode* scopingNode)
 {
     TreeScope& treeScope = element->treeScope();
 
     // [skipped, because already checked] a) it's a UA rule
-    // b) element is allowed to apply author rules
-    if (elementApplyAuthorStyles)
-        return true;
+    // [skipped, because already checked] b) element is not in shadow tree
     // c) the rules comes from a scoped style sheet within the same tree scope
     if (!scopingNode || treeScope == scopingNode->treeScope())
         return true;
@@ -135,11 +133,15 @@ static bool rulesApplicableInCurrentTreeScope(const Element* element, const Cont
     return false;
 }
 
-void ElementRuleCollector::collectMatchingRules(const MatchRequest& matchRequest, RuleRange& ruleRange, SelectorChecker::ContextFlags contextFlags, CascadeScope cascadeScope, CascadeOrder cascadeOrder)
+void ElementRuleCollector::collectMatchingRules(const MatchRequest& matchRequest, RuleRange& ruleRange, CascadeScope cascadeScope, CascadeOrder cascadeOrder)
 {
     ASSERT(matchRequest.ruleSet);
     ASSERT(m_context.element());
 
+    SelectorChecker::ContextFlags contextFlags = SelectorChecker::DefaultBehavior;
+    if (matchRequest.isInShadowTree)
+        contextFlags = SelectorChecker::ScopeContainsLastMatchedElement;
+
     Element& element = *m_context.element();
     const AtomicString& pseudoId = element.shadowPseudoId();
     if (!pseudoId.isEmpty()) {
@@ -151,12 +153,12 @@ void ElementRuleCollector::collectMatchingRules(const MatchRequest& matchRequest
         collectMatchingRulesForList(matchRequest.ruleSet->cuePseudoRules(), contextFlags, cascadeScope, cascadeOrder, matchRequest, ruleRange);
     // Check whether other types of rules are applicable in the current tree scope. Criteria for this:
     // a) it's a UA rule
-    // b) the tree scope allows author rules
+    // b) the tree scope is not shadow tree
     // c) the rules comes from a scoped style sheet within the same tree scope
     // d) the rules comes from a scoped style sheet within an active shadow root whose host is the given element
     // e) the rules can cross boundaries
-    // b)-e) is checked in rulesApplicableInCurrentTreeScope.
-    if (!m_matchingUARules && !rulesApplicableInCurrentTreeScope(&element, matchRequest.scope, matchRequest.elementApplyAuthorStyles))
+    // c)-e) is checked in rulesApplicableInCurrentTreeScope.
+    if (!m_matchingUARules && matchRequest.isInShadowTree && !rulesApplicableInCurrentTreeScope(&element, matchRequest.scope))
         return;
 
     // We need to collect the rules for id, class, tag, and everything else into a buffer and