Selectors in styles in shadowRoots should match in all of the host's shadowRoots.

Source/core/css/resolver/ScopedStyleTree.h

Index: Source/core/css/resolver/ScopedStyleTree.h
diff --git a/Source/core/css/resolver/ScopedStyleTree.h b/Source/core/css/resolver/ScopedStyleTree.h
index 51f68fe70d7c2abb0165a1315d4d37e004309b20..062c6d7156a439391c9f2af6e80ac4ebf9187ae2 100644
--- a/Source/core/css/resolver/ScopedStyleTree.h
+++ b/Source/core/css/resolver/ScopedStyleTree.h
@@ -55,9 +55,8 @@ public:
     ScopedStyleResolver* scopedStyleResolverForDocument() const { return m_scopedResolverForDocument; }
 
     void resolveScopedStyles(const Element*, Vector<ScopedStyleResolver*, 8>&);
-    void collectScopedResolversForHostedShadowTrees(const Element*, Vector<ScopedStyleResolver*, 8>&);
     void resolveScopedKeyframesRules(const Element*, Vector<ScopedStyleResolver*, 8>&);
-    ScopedStyleResolver* scopedResolverFor(const Element*);
+    ScopedStyleResolver* scopedResolverFor(const ContainerNode*);
 
     void remove(const ContainerNode* scopingNode);
 
@@ -69,6 +68,7 @@ public:
     bool buildInDocumentOrder() const { return m_buildInDocumentOrder; }
 
 private:
+    ContainerNode* traverseParent(const ContainerNode*) const;
     void setupScopedStylesTree(ScopedStyleResolver* target);
 
     bool cacheIsValid(const ContainerNode* parent) const { return parent && parent == m_cache.nodeForScopedStyles; }
@@ -95,10 +95,10 @@ private:
     ScopedStyleCache m_cache;
 };
 
-inline ScopedStyleResolver* ScopedStyleTree::scopedResolverFor(const Element* element)
+inline ScopedStyleResolver* ScopedStyleTree::scopedResolverFor(const ContainerNode* node)
 {
-    if (!cacheIsValid(element))
-        resolveStyleCache(element);
+    if (!cacheIsValid(node))
+        resolveStyleCache(node);
 
     return m_cache.scopedResolver;
 }