Recompute slow scroll regions after overflow recalc

Source/core/page/scrolling/ScrollingCoordinator.h

Index: Source/core/page/scrolling/ScrollingCoordinator.h
diff --git a/Source/core/page/scrolling/ScrollingCoordinator.h b/Source/core/page/scrolling/ScrollingCoordinator.h
index 7838814eec051f094069e535a993cba793442d9b..b53d405c7ea20d3023b3bca8e581c30438b2a2db 100644
--- a/Source/core/page/scrolling/ScrollingCoordinator.h
+++ b/Source/core/page/scrolling/ScrollingCoordinator.h
@@ -65,6 +65,8 @@ public:
 
     // Called when any frame has done its layout.
     void notifyLayoutUpdated();
+    // Called when any frame recalculates its overflows after style change.
+    void notifyOverflowUpdated();
 
     void updateAfterCompositingChangeIfNeeded();