Make right-most compound check explicit.

Source/core/css/SelectorChecker.h

Index: Source/core/css/SelectorChecker.h
diff --git a/Source/core/css/SelectorChecker.h b/Source/core/css/SelectorChecker.h
index 62291e12a5a8526f89c43e66c9495a4720fd984b..03c996fafb7918f37afc999b3adf69bb28e8f530 100644
--- a/Source/core/css/SelectorChecker.h
+++ b/Source/core/css/SelectorChecker.h
@@ -59,10 +59,11 @@ public:
             , scope(nullptr)
             , visitedMatchType(visitedMatchType)
             , pseudoId(NOPSEUDO)
-            , elementStyle(0)
+            , elementStyle(nullptr)
             , scrollbar(nullptr)
             , scrollbarPart(NoPart)
             , isSubSelector(false)
+            , inRightmostCompound(true)
             , hasScrollbarPseudo(false)
             , hasSelectionPseudo(false)
             , isUARule(false)
@@ -81,6 +82,7 @@ public:
         RawPtrWillBeMember<LayoutScrollbar> scrollbar;
         ScrollbarPart scrollbarPart;
         bool isSubSelector;
+        bool inRightmostCompound;
         bool hasScrollbarPseudo;
         bool hasSelectionPseudo;
         bool isUARule;