Hovered/active/focused nodes will never share style with siblings/cousins.

Source/core/css/resolver/StyleResolver.cpp

Index: Source/core/css/resolver/StyleResolver.cpp
diff --git a/Source/core/css/resolver/StyleResolver.cpp b/Source/core/css/resolver/StyleResolver.cpp
index dd3d7c788119c5b2549d12b25395b5187b83262b..1647e2d38d1e3f3ecc680dfacdc308fb36c00953 100644
--- a/Source/core/css/resolver/StyleResolver.cpp
+++ b/Source/core/css/resolver/StyleResolver.cpp
@@ -783,6 +783,15 @@ RenderStyle* StyleResolver::locateSharedStyle()
     // Ids stop style sharing if they show up in the stylesheets.
     if (state.styledElement()->hasID() && m_features.idsInRules.contains(state.styledElement()->idForStyleResolution().impl()))
         return 0;
+    // Active and hovered elements always make a chain towards the document node
+    // and no siblings or cousins will have the same state.
+    if (state.styledElement()->hovered())
+        return 0;
+    if (state.styledElement()->active())
+        return 0;
+    // There is always only one focused element.
+    if (state.styledElement()->focused())
+        return 0;
     if (parentElementPreventsSharing(state.element()->parentElement()))
         return 0;
     if (state.styledElement()->hasScopedHTMLStyleChild())