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

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 66036b00ca3f603063beb90ebe945d5270f8b2f3..45ba04a19c15018c6be50a8794b852546406d9af 100644
--- a/Source/core/css/ElementRuleCollector.cpp
+++ b/Source/core/css/ElementRuleCollector.cpp
@@ -378,9 +378,6 @@ static inline bool compareRules(const MatchedRule& matchedRule1, const MatchedRu
     if (specificity1 != specificity2)
         return specificity1 < specificity2;
 
-    if (matchedRule1.styleSheetIndex() != matchedRule2.styleSheetIndex())
-        return matchedRule1.styleSheetIndex() < matchedRule2.styleSheetIndex();
-
     return matchedRule1.position() < matchedRule2.position();
 }