Invalidate CustomScrollbars on having window-inactive selector.

Source/core/dom/StyleEngine.cpp

Index: Source/core/dom/StyleEngine.cpp
diff --git a/Source/core/dom/StyleEngine.cpp b/Source/core/dom/StyleEngine.cpp
index 49708dcd1b16befc79881cde65483bba7dfc6c0d..a557562c8e6134ba755f14b94977e0ee012bc708 100644
--- a/Source/core/dom/StyleEngine.cpp
+++ b/Source/core/dom/StyleEngine.cpp
@@ -61,6 +61,7 @@ StyleEngine::StyleEngine(Document& document)
     , m_documentScopeDirty(true)
     , m_usesSiblingRules(false)
     , m_usesFirstLineRules(false)
+    , m_usesWindowInactiveSelector(false)
     , m_usesFirstLetterRules(false)
     , m_usesRemUnits(false)
     , m_maxDirectAdjacentSelectors(0)
@@ -217,6 +218,7 @@ void StyleEngine::combineCSSFeatureFlags(const RuleFeatureSet& features)
     // Delay resetting the flags until after next style recalc since unapplying the style may not work without these set (this is true at least with before/after).
     m_usesSiblingRules = m_usesSiblingRules || features.usesSiblingRules();
     m_usesFirstLineRules = m_usesFirstLineRules || features.usesFirstLineRules();
+    m_usesWindowInactiveSelector = m_usesWindowInactiveSelector || features.usesWindowInactiveSelector();
     m_maxDirectAdjacentSelectors = max(m_maxDirectAdjacentSelectors, features.maxDirectAdjacentSelectors());
 }
 
@@ -224,6 +226,7 @@ void StyleEngine::resetCSSFeatureFlags(const RuleFeatureSet& features)
 {
     m_usesSiblingRules = features.usesSiblingRules();
     m_usesFirstLineRules = features.usesFirstLineRules();
+    m_usesWindowInactiveSelector = features.usesWindowInactiveSelector();
     m_maxDirectAdjacentSelectors = features.maxDirectAdjacentSelectors();
 }