Invalidate CustomScrollbars on having window-inactive selector.

Source/core/dom/StyleEngine.h

Index: Source/core/dom/StyleEngine.h
diff --git a/Source/core/dom/StyleEngine.h b/Source/core/dom/StyleEngine.h
index f57496febc67f7596819474b0ec10e2deba604bf..dc34d518f7e3cbbc97c23607c7cc01326603774d 100644
--- a/Source/core/dom/StyleEngine.h
+++ b/Source/core/dom/StyleEngine.h
@@ -121,6 +121,8 @@ public:
     unsigned maxDirectAdjacentSelectors() const { return m_maxDirectAdjacentSelectors; }
     bool usesSiblingRules() const { return m_usesSiblingRules; }
     bool usesFirstLineRules() const { return m_usesFirstLineRules; }
+    bool usesWindowInActiveSelector() const { return m_usesWindowInActiveSelector; }
+
     bool usesFirstLetterRules() const { return m_usesFirstLetterRules; }
     void setUsesFirstLetterRules(bool b) { m_usesFirstLetterRules = b; }
     bool usesRemUnits() const { return m_usesRemUnits; }
@@ -282,6 +284,7 @@ private:
 
     bool m_usesSiblingRules;
     bool m_usesFirstLineRules;
+    bool m_usesWindowInActiveSelector;
     bool m_usesFirstLetterRules;
     bool m_usesRemUnits;
     unsigned m_maxDirectAdjacentSelectors;