Recompute slow scroll regions after overflow recalc

Source/core/page/scrolling/ScrollingCoordinator.cpp

Index: Source/core/page/scrolling/ScrollingCoordinator.cpp
diff --git a/Source/core/page/scrolling/ScrollingCoordinator.cpp b/Source/core/page/scrolling/ScrollingCoordinator.cpp
index 96c99893920d41e6b2880c2235d9abc580f85bd4..ee39d6115d4c8a0c0464877d4510c3fbb90a65ac 100644
--- a/Source/core/page/scrolling/ScrollingCoordinator.cpp
+++ b/Source/core/page/scrolling/ScrollingCoordinator.cpp
@@ -129,6 +129,11 @@ void ScrollingCoordinator::notifyLayoutUpdated()
     m_shouldScrollOnMainThreadDirty = true;
 }
 
+void ScrollingCoordinator::notifyOverflowUpdated()
+{
+    m_scrollGestureRegionIsDirty = true;
+}
+
 void ScrollingCoordinator::scrollableAreasDidChange()
 {
     ASSERT(m_page);