Layout overflow from transforms should update frame scrollbars

Source/platform/scroll/ScrollView.h

Index: Source/platform/scroll/ScrollView.h
diff --git a/Source/platform/scroll/ScrollView.h b/Source/platform/scroll/ScrollView.h
index aa81e2cb0a32b3858d283b9c5ca304bfd281f6ea..f19d07759c13e6140bacf5450cd8ff7be4dddff5 100644
--- a/Source/platform/scroll/ScrollView.h
+++ b/Source/platform/scroll/ScrollView.h
@@ -35,6 +35,7 @@
 #include "platform/scroll/Scrollbar.h"
 
 #include "wtf/HashSet.h"
+#include "wtf/TemporaryChange.h"
 
 namespace WebCore {
 
@@ -294,6 +295,15 @@ protected:
 
     IntSize excludeScrollbars(const IntSize&) const;
 
+    class InUpdateScrollbarsScope {
+    public:
+        explicit InUpdateScrollbarsScope(ScrollView* view)
+            : m_scope(view->m_inUpdateScrollbars, true)
+        { }
+    private:
+        TemporaryChange<bool> m_scope;
+    };
+
 private:
     bool adjustScrollbarExistence(ComputeScrollbarExistenceOption = FirstPass);