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 88cb5374019492929b6536d1864a256ab31376c7..4912a8c27f35efdffa27b67804ba41edd30ab1a0 100644
--- a/Source/core/page/scrolling/ScrollingCoordinator.cpp
+++ b/Source/core/page/scrolling/ScrollingCoordinator.cpp
@@ -137,6 +137,11 @@ void ScrollingCoordinator::notifyLayoutUpdated()
     m_shouldScrollOnMainThreadDirty = true;
 }
 
+void ScrollingCoordinator::notifyOverflowUpdated()
+{
+    m_scrollGestureRegionIsDirty = true;
+}
+
 void ScrollingCoordinator::scrollableAreasDidChange()
 {
     ASSERT(m_page);