Change shadow style's scope from Shadow Host to Shadow Root

Source/core/css/SelectorChecker.cpp

Index: Source/core/css/SelectorChecker.cpp
diff --git a/Source/core/css/SelectorChecker.cpp b/Source/core/css/SelectorChecker.cpp
index fab750f124da13a2209bad1a0073bdc62821e2d4..339598720ed3a329f9be3994a3242b79e71aa153 100644
--- a/Source/core/css/SelectorChecker.cpp
+++ b/Source/core/css/SelectorChecker.cpp
@@ -83,8 +83,8 @@ Element* SelectorChecker::parentElement(const SelectorCheckingContext& context,
     if (allowToCrossBoundary)
         return context.element->parentOrShadowHostElement();
 
-    // If context.scope is a shadow host, we should walk up from a shadow root to its shadow host.
-    if ((context.behaviorAtBoundary & SelectorChecker::ScopeIsShadowHost) && context.scope == context.element->shadowHost())
+    // If context.scope is a shadow root, we should walk up to its shadow host.
+    if ((context.behaviorAtBoundary & SelectorChecker::ScopeIsShadowRoot) && context.scope == context.element->containingShadowRoot())
         return context.element->parentOrShadowHostElement();
 
     if ((context.behaviorAtBoundary & SelectorChecker::BoundaryBehaviorMask) != SelectorChecker::StaysWithinTreeScope)
@@ -106,12 +106,12 @@ bool SelectorChecker::scopeContainsLastMatchedElement(const SelectorCheckingCont
         return true;
 
     ASSERT(context.scope);
-    // If behaviorAtBoundary is not ScopeIsShadowHost, we can use "contains".
-    if (!(context.behaviorAtBoundary & SelectorChecker::ScopeIsShadowHost))
+    // If behaviorAtBoundary is not ScopeIsShadowRoot, we can use "contains".
+    if (!(context.behaviorAtBoundary & SelectorChecker::ScopeIsShadowRoot))
         return context.scope->contains(context.element);
 
     // If a given element is scope, i.e. shadow host, matches.
-    if (context.element == context.scope && (!context.previousElement || context.previousElement->isInDescendantTreeOf(context.element)))
+    if (context.element == context.scope->shadowHost() && (!context.previousElement || context.previousElement->isInDescendantTreeOf(context.element)))
         return true;
 
     ShadowRoot* root = context.element->containingShadowRoot();
@@ -119,16 +119,14 @@ bool SelectorChecker::scopeContainsLastMatchedElement(const SelectorCheckingCont
         return false;
 
     // If a host of the containing shadow root is scope, matches.
-    return root->host() == context.scope;
+    return root == context.scope;
 }
 
 static inline bool nextSelectorExceedsScope(const SelectorChecker::SelectorCheckingContext& context)
 {
-    if ((context.behaviorAtBoundary & SelectorChecker::BoundaryBehaviorMask) != SelectorChecker::StaysWithinTreeScope)
-        return context.element == context.scope;
-
     if (context.scope && context.scope->isInShadowTree())
-        return context.element == context.scope->containingShadowRoot()->host();
+        return context.element == context.scope->shadowHost();
+
     return false;
 }
 
@@ -342,7 +340,7 @@ SelectorChecker::Match SelectorChecker::matchForRelation(const SelectorCheckingC
     case CSSSelector::ShadowPseudo:
         {
             // If we're in the same tree-scope as the scoping element, then following a shadow descendant combinator would escape that and thus the scope.
-            if (context.scope && context.scope->treeScope() == context.element->treeScope() && (context.behaviorAtBoundary & BoundaryBehaviorMask) != StaysWithinTreeScope)
+            if (context.scope && context.scope->shadowHost() && context.scope->shadowHost()->treeScope() == context.element->treeScope() && (context.behaviorAtBoundary & BoundaryBehaviorMask) != StaysWithinTreeScope)
                 return SelectorFailsCompletely;
 
             Element* shadowHost = context.element->shadowHost();
@@ -389,15 +387,16 @@ SelectorChecker::Match SelectorChecker::matchForShadowDistributed(const Element*
     for (size_t i = 0; i < insertionPoints.size(); ++i) {
         nextContext.element = insertionPoints[i];
 
-        // If a given scope is a shadow host of an insertion point but behaviorAtBoundary doesn't have ScopeIsShadowHost,
+        // If a given scope is a shadow host of an insertion point but behaviorAtBoundary doesn't have ScopeIsShadowRoot,
         // we need to update behaviorAtBoundary to make selectors like ":host > ::content" work correctly.
         if (m_mode == SharingRules) {
-            nextContext.behaviorAtBoundary = static_cast<BehaviorAtBoundary>(behaviorAtBoundary | ScopeIsShadowHost);
-            nextContext.scope = insertionPoints[i]->containingShadowRoot()->shadowHost();
-        } else if (scope == insertionPoints[i]->containingShadowRoot()->shadowHost() && !(behaviorAtBoundary & ScopeIsShadowHost))
-            nextContext.behaviorAtBoundary = static_cast<BehaviorAtBoundary>(behaviorAtBoundary | ScopeIsShadowHost);
-        else
+            nextContext.behaviorAtBoundary = static_cast<BehaviorAtBoundary>(behaviorAtBoundary | ScopeIsShadowRoot);
+            nextContext.scope = insertionPoints[i]->containingShadowRoot();
+        } else if (scope == insertionPoints[i]->containingShadowRoot() && !(behaviorAtBoundary & ScopeIsShadowRoot)) {
+            nextContext.behaviorAtBoundary = static_cast<BehaviorAtBoundary>(behaviorAtBoundary | ScopeIsShadowRoot);
+        } else {
             nextContext.behaviorAtBoundary = behaviorAtBoundary;
+        }
 
         nextContext.isSubSelector = false;
         nextContext.elementStyle = 0;
@@ -537,7 +536,8 @@ bool SelectorChecker::checkOne(const SelectorCheckingContext& context, const Sib
     bool elementIsHostInItsShadowTree = isHostInItsShadowTree(element, context.behaviorAtBoundary, context.scope);
 
     // Only :host and :ancestor should match the host: http://drafts.csswg.org/css-scoping/#host-element
-    if (elementIsHostInItsShadowTree && !selector.isHostPseudoClass())
+    if (elementIsHostInItsShadowTree && !selector.isHostPseudoClass()
+        && !(context.behaviorAtBoundary & TreatShadowHostAsNormalScope))
         return false;
 
     if (selector.match() == CSSSelector::Tag)
@@ -929,7 +929,7 @@ bool SelectorChecker::checkOne(const SelectorCheckingContext& context, const Sib
                 // :host only matches a shadow host when :host is in a shadow tree of the shadow host.
                 if (!context.scope)
                     return false;
-                const ContainerNode* shadowHost = (context.behaviorAtBoundary & ScopeIsShadowHost) ? context.scope : (context.scope->isInShadowTree() ? context.scope->shadowHost() : 0);
+                const ContainerNode* shadowHost = context.scope->shadowHost();
                 if (!shadowHost || shadowHost != element)
                     return false;
                 ASSERT(element.shadow());
@@ -947,7 +947,7 @@ bool SelectorChecker::checkOne(const SelectorCheckingContext& context, const Sib
                 // If one of simple selectors matches an element, returns SelectorMatches. Just "OR".
                 for (subContext.selector = selector.selectorList()->first(); subContext.selector; subContext.selector = CSSSelectorList::next(*subContext.selector)) {
                     subContext.behaviorAtBoundary = ScopeIsShadowHostInPseudoHostParameter;
-                    subContext.scope = shadowHost;
+                    subContext.scope = context.scope;
                     // Use NodeRenderingTraversal to traverse a composed ancestor list of a given element.
                     Element* nextElement = &element;
                     SelectorCheckingContext hostContext(subContext);